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Techniques of Radiotherapy
in Oral Cancer
INDIAN DENTAL ACADEMY
Leader in continuing Dental
Contents
 History
 Radiation Physics
 Radiation biology
 Altered fractionation therapy
 General concepts of Radiother...
 Radiation Oncology is a medical specialty that focuses predominantly on
treatment of Neoplastic diseases with the use of...
History
 Sir Wilhelm Conrad Roentgen discovered x-rays on 8th November
1895
 In 1898 Madam Curie discovered radium.
 In...
 Major & rapid advance in radiotherapy – Development of CO60
Teletherapy, Linear Accelerator, Mega Voltage therapy and
Su...
Radiation Physics
 Radiation is transmission of energy through space and matter.
 There are two types of Therapeutic Rad...
 High energy X- rays and Gamma rays are used most often in radiation
therapy
 These electromagnetic radiation subtypes d...
X-rays
 X-rays are created by linear accelerators (linacs).
- which involve an electrical input that causes a filament to...
Gamma - rays
 Gamma rays are produced by materials such as radium, uranium, cobalt60
 These materials undergo radioactiv...
Particle therapy
 This type of therapy differs from photon radiotherapy in that it involves the
use of fast-moving subato...
Electron Therapy
 Small, negatively charged particles
 These are accelerated to high energy(upto 50 MeV) by means of lin...
Electron Beam Therapy Machines
 Kilovoltage Machines
 Linear Accelerators
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Kilovoltage Machines
 Earliest X- ray machines used in treatment of cancer
 Generate low energy radiates from 50 kV-100 ...
Linear Accelerators (linacs)
 High energy X ray machines
 In electron mode of linac opertion, the electon beam is direct...
Proton therapy
 Protons are positively charged particles, its mass is 1835 times greater
than electrons.
 Essentially it...
Neutron beam therapy
 Large, neutral particles with high linear energy transfer (LET) - thus
producing denser ionization ...
Absorbed dose
 Is a ratio between the average amount of energy (E) deposited in a small
volume with mass(M).
- Older unit...
How Does Radiation Act ??
 Absorption of the energy (electromagnetic or particulate radiation) in the
body produces a min...
 In particle radiation
- electrons entering tissues undergo either elastic or inelastic collision
with electrons or atoms...
Radiation biology
 Ionization radiation delivered to cells or tissues initiates a chain of events
based on energy and typ...
 Sparsely ionizing radiation , such as X- rays or gamma rays, induce
damage mainly through Indirect effects
 Densely ion...
Effects On Cell Kinetics
 Radiation affects the expression of cyclins and cyclin dependent kinases.
 These are group of ...
 Although ionization radiation can affect tissue through many mechanisms,
depending on the size of the dose.
 Cell killi...
Mitotic (Reproductive) death
 Dominant mode of cell killing in radiotherapy
 Cells die when they attempt to divide.
 At...
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Cell death by Apoptosis
 Usually occurs within hours of radiation exposure.
 Typically seen in after lower radiation dos...
Factors affecting radiation sensitivity
 Many factors affect the sensitivity of normal and malignant cells and the
respon...
Oxygen status
 The ability of ionizing radiation to cause biologic change is very much
dependent on the amount of oxygen ...
Cell age in in the division cycle
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Type of radiation
 Different type of radiation induce different densities of ionization or energy
deposition per unit len...
Dose
 The Radiation Therapy Oncology Group (RTOG) has conducted a dose-
searching study to determine the maximum dose tha...
 Between 66 and 70 Gy are usually prescribed for primary tumors
measuring 2 cm or less.
 When radiotherapy alone is deli...
Radiobiological Basis of Fractionation
 Use of multiple fractions over many weeks of radiation therapy is based
on the pr...
Radiobiological Basis of Fractionation
 Repair
 Re-oxygenation
 Repopulation
 Redistribution
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Repair of sublethal cells
 Fractionation helps in recovery of sub lethally damaged cells.
 The repair capacity varies am...
Repopulation (Regeneration)
 Depletion of cells (during therapy), in both normal & neoplastic tissues,
triggers a regener...
Redistribution
 In initially asynchronous cell population , the 1st
radiation dose
preferentially kills cells in sensitiv...
Reoxygenation
 Bulky tumors may have centers that relatively hypoxic due to their
location away from a blood vessel
 Tum...
 This process(reoxygenation) results from a number of mechanisms, such
as:
- the preferential elimination of more radiose...
Altered Fractionation Techniques For Radiation
Therapy
 Wilhers identified hazard of accelerated tumour clonogen repopulation
during conventional once-a-day radiation therapy a...
Altered fractionation stratergies
A) Hyperfractionation
- Decreased fraction size
- Increased fraction number
- Increased ...
 Strategy of Hyperfractionation is to use an increased no. of smaller
doses per fraction than conventional 1.8 - 2.0 Gy p...
B) Acceleration Fractionation
 Decrease in overall treatment time
- Maintain or slightly reduce
- Fraction size
- Fractio...
Newer Regime
Continous Hyper Fractionated Accelerated Radiation Therapy (CHART)
54 Gy in 36 fractions – 1.5 Gy T.I.D. over...
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Indications for Radiotherapy
Indications for Radiotherapy
 T1-T2 lesions
 T3,T4 Locally advanced lesions
- Post surgical treatment
- Only therapy if ...
General Concept Of Radiotherapeutic Techniques
Treatment planning
 Radiation treatment plan is based on tumor site, tumor size, the total
volume to be radiated , the nu...
Patient positioning & Immobilization
 Radiotherapy can be delivered in supine, prone or even sitting position
 Immobiliz...
Patient positioning and immobilization devices are used to
achieve true reproducibility and accuracy in set up.
Head Frame...
Simulation & Beam verification
 Simulator is an isocentrically mounted diagnostic X-ray unit that mimics
geometrical arra...
Techniques of Radiotherapy
Clinical Radiotherapy Techniques
Brachytherapy Teletherapy
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Brachytherapy
 Brachio in greek means short range
 Brachytherapy is the sub specialty of radiation oncology
which uses s...
 Two types of implants:
Removable Implants:
Radium, Tantalum, I 125
& Ir 192
& Co60
Permanent Implants: (left insitu to d...
Here radioactive sources are implanted into the tumor for definite period
(temporary implants) or indefinitely (permanent)...
Intracavitary brachytherapy
 Treatment by placement of radioactive sources inside natural body
cavities.
 Mainly used in...
Advantages:
 Ideally suited for anatomical locations where tumor is well localised to
tissues (Anterior part of tongue)
...
Dose:
 Typically, about 3.0 to 3.5 Gy is given to a distance of about 1 cm ( from the
periphery of the catheters), and tw...
Radioactive Isotopes
 Systemic radiation in which isotopes are injected IV
 Useful therapeutic effects can be obtained i...
Teletherapy (External beam thearpy)
 “Tele” means far or distant
 Here beam comes from a source located at a distance fr...
Contact therapy
 Contact therapy operates at potentials of 40-50 kV and tube current of
2mA.
 Facilitates irradiation of...
Superficial therapy
 Term superficial therapy applies to treatment with x-rays produced at a
energy ranging from 50 to 15...
Orthovoltage or deep therapy
 Term orthovoltage therapy is used to describe treatment with x-rays
ranging from 150 – 500 ...
Megavoltage therapy
 X-ray beams of energy 1 MV or greater can be classified as megavoltage
beams
 The term strictly app...
The Radiotherapeutic Techniques
 Single field arrangement
 Parallel opposed fields
 Wedge lateral field
 Multiple fiel...
Single Field Arrangement
 Tumor is treated with one field only
 Quick & easily reproducible therapy
Parallel opposed fie...
Radiation fields
Lateral field Antero Posterior Field
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Wedge lateral field
 Two right angled fields can be combined to irradiate a discrete tumor
volume rather than placing the...
 Moving field techniques which are modifications of multiple field therapy
 Radiation source rotates around the tumor is...
Methods to Reduce Side Effects:
 Collimation/filtration
 Fractionation of dose
 Use of high LET radiation
 Chemical ra...
Combined Therapy: Multimodality
Therapy
Preoperative Radiotherapy
Advantages:
 Eradicate subclinical disease beyond resection margins
 Prevention of marginal re...
 Dosage
 180 to 200 cGy/ fraction
1 fraction/day ;5 days/ wk, to a total dosage of 5,000 to 6,000 cGy
After completion o...
Disadvantages
 Diminished wound healing
 Delay of definitive surgery
 Can’t cure already developed occult distant metas...
Post operative Radiotherapy
 Indications
- When estimated risk of loco regional recurrence is > 20 %
- Advanced T3 or T4 ...
Drawbacks of Post operative Radiotherapy
- Delay in initiation of radiation therapy due to wound complications from
surger...
Concomitant Chemoradiotherapy
 Unresectable disease to improve local & regional control
 Mechanism for interaction b/w c...
Multiple Agents & Radiotherapy
 Improved survival time- primary goal
 Combining several drugs with radiation- Acute toxi...
Advances in Radiotherapy
Modification Of Tumor Hypoxia
 Cellular Hypoxia is considered as an important factor in control of head &
neck cancer
 M...
Hyperbaric oxygen therapy
 Oxygen under high pressure is given to the patient
 Usually given as 20-30 dives at 100% oxyg...
Hypoxic Cell Sensitizers
 Group of Bioreductive Nitroimidazole drugs which mimic oxygen
 Selectively Radiosensitised hyp...
Tirapazamine
 New bioreductive agent
 Undergo selective electron reduction in hypoxic conditions, forming free
radicals,...
Radio protectors
 Amifistone (Ethyol)- sulfhydryl compound that acts as potent scavenger of
free radicals generated in ti...
Conventional external beam radiotherapy
 Conventional external beam radiotherapy (2DXRT) is delivered via two-
dimensiona...
Conformal Radiotherapy
 Conformal radiotherapy is also called 3D conformal radiotherapy (3DCRT).
 It uses a special way ...
Intensity Modulated Radiotherapy
 Like conformal radiotherapy, IMRT shapes the radiation beams to closely
fit the area wh...
 IMRT is done with Linear accelerator (LINAC) with multi-leaf collimator
that moves around the patient and shapes the bea...
Image-guided radiation therapy (IGRT)
 Traditionally, imaging technology has been used to produce three-
dimensional scan...
 IGRT combines scanning and radiation equipment,
- i.e IGRT uses a linear accelerator (IMRT), equipped with a kilovoltage...
Hyperthermia & Radiation Therapy
 Supra normal temperature in the range of 41-430
C sensitizes cells to
radiation.
 It s...
Radioimmunotherapy
 Use of radio labeled antibodies to deliver doses of radiation directly to the
cancer site
 Antibodie...
 Once injected into the body, the antibodies actively seek out the cancer
cells, which are destroyed by the cell-killing ...
TREATMENT OF RECCURENCE
 90% of the recurrence occurs within 2 years.
 8% of recurrence occurs after 5 years. In such ca...
THE ROLE OF RADIATION THERAPY ALONE FOR
HEAD AND NECK TUMOR - BY SITE
Lip
 T1 to T2 lip cancers - Surgery / radiation therapy can be considered for
primary treatment of based on specific anat...
Oral cavity
 For early T1 & T2 lesions - radiation therapy & surgery are equally
effective in achieving local control.
 ...
 For moderately advanced T2 to T3 lesions, full course external beam
radiation therapy is used.
 For lesions in the floo...
Floor of Mouth
 T1 & T2 lesions can be treated - surgery / radiation therapy.
 T1 & T2 lesions + clinically positive nod...
Tongue
 T1 and T2 lesions can be treated with surgery / radiation therapy.
 Primary radiation therapy - dosage of 4,000 ...
Base of Tongue
 T1 and T2 lesions can be successfully treated by either surgery or
radiation therapy.
 Majority of patie...
• Following a 3-week break - iridium 192 temporary
interstitiary implant ionto the base of the tongue
delivering 2,400 to ...
Salivary glands
 Surgery is the treatment of choice for both primary and locally recurrent
salivary gland tumors.
 For u...
 Dosage: 6 MV x-rays are administered,
 If the treatment is postoperative, 180 cGy per fraction is given to a total
dosa...
Pre Irradiation Dental Care
 Extraction of unrestorable teeth & those with advanced periodontal
disease
 Extractions don...
Post-treatment Protocol
 Regular application of fluorides & regular check up
 Salivary substitutes for salivary dysfunct...
Complication of Radiotherapy
 Under 3,000 cGy — Mucositis, candidiasis, xerostomia & dysgeusia begin
 Over 3,000 cGy - xerostomia (permanent) and tas...
 Progressive muscle fibrosis may limit the neck and shoulder function.
Some times trismus may also seen.
 Visual impairm...
Sequelae of radiation therapy
ORN
Oral candidiasis
Xerostomia
Soft tissue fibrosis
Trismus
Obliterative endartritis
Slow/ ...
Mucositis
 The oral mucous membrane consists of
Basal layer composed of radiosensitive vegetative & differentiating
inter...
 After irradiation is completed, mucosa begins to heal rapidly
 Healing is complete by about 2 months
 After months to ...
Clinical features
 The early clinical sign of mucositis is Erythema presenting about
4–5 days following cumulative doses ...
Management Of Mucositis
Oral care & Topical therapy:
 Bland oral rinses & topical anesthetics
 Saline, Bicarbonate
 Lub...
Management Of Mucositis
Methods to reduce exposure of the mucosa to damaging agents
 Ice chips
 Propantheline
Antimicrob...
Anti-inflammatory medications
Biologic response modifiers
 Interleukin-1,11
 GM-CSF
 G-CSF
 Keratinocyte growth factor...
Cytoprotective agents
 Amifostine
 Benzydamine
 Glutamine
 N-acetyl cysteine
 Prostaglandins
 Vitamin E
Low-energy l...
Oral candidiasis
• A fair number of patients will develop an oral Candida
infection .
• May be asymptomatic / may complain...
Taste buds
 Extensive degeneration of normal histological architecture of taste buds
 Hypoguesia, Aguesia & Dysguesia
 ...
Salivary glands
 Parenchymal component is radiosensitive
 Extent of reduced salivary flow is dose dependent
 Reaches ze...
Management of Xerostomia
 Preventive therapy
( Topical Fluorides , Regular dental visits )
 Symptomatic treatment
(sippi...
SIALOGOGUES
Mechanical stimulants
 Eating foods which require Mastication
 Artificial Sweeteners
Chemical stimulants
 M...
Proposed Systemic Sialogogues
 Pilocarpine
 Cevimeline
 Bethanechol
 Anetholetrithione
 Guaifensin
 Bromhexine
 Neo...
Radiation caries
 Rampant from of dental caries
 Due to exposure of salivary glands to therapeutic irradiation
 Reduced...
Clinically 3 types are present:
 Widespread superficial lesions attacking all surfaces
 Involving primarily cementum & d...
Radiation caries
Osteoradionecrosis
 Primary damage to mature bone results from radiation induced damage to
vasculature of periosteum & co...
Pathogenesis
Therapeutic irradiation
Endothelial death, thrombosis, hyalinization of BV
Progressive obliterative endarteri...
Clinical features
 Severe, deep, boring pain for weeks to months
 Soft tissue abscesses
 Persistently draining sinus
 ...
Therapeutic Modalities To Decrease Incidence Of
ORN
 Dose fractionation
 Use of megavoltage
 Meticulous collimation
 s...
Management
 Debridement
 Antibiotics to control secondary infection
 Hydration, fluid therapy
 Narcotics
 Sequestrect...
Reference
 Text book of Radiation Oncology – Principles and Practice
Goura K Rath, Bindhu K Mohanti
 Text of Oral Medici...
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Techniques of Radiotherapy in Oral Cancer / dental courses

  1. 1. Techniques of Radiotherapy in Oral Cancer INDIAN DENTAL ACADEMY Leader in continuing Dental
  2. 2. Contents  History  Radiation Physics  Radiation biology  Altered fractionation therapy  General concepts of Radiotherapeutic technique  Techniques of Radiotherapy  Advances in Radiotherapy  Role of Radiation therapy for H & N tumors - BY SITE  Dental care of the patients receiving radiation  Complications & management www.indiandentalacademy.com
  3. 3.  Radiation Oncology is a medical specialty that focuses predominantly on treatment of Neoplastic diseases with the use of ionizing radiation given either alone or in combination with surgery, chemotherapy or both.  Radiotherapy ( Radiation therapy) is the treatment of diseases with ionizing radiation.  It is one of the principle mode of management of head & neck carcinomas as these tumors are radiosensitive. www.indiandentalacademy.com
  4. 4. History  Sir Wilhelm Conrad Roentgen discovered x-rays on 8th November 1895  In 1898 Madam Curie discovered radium.  In the beginning of 20th century high single dose radiation was used by Dermatologists and Surgeons as a form of cautery.  In 1920- Fractionation of Radiotherapy was introduced by Thames and Hendry and radiation was accepted as a modality of treating cancers www.indiandentalacademy.com
  5. 5.  Major & rapid advance in radiotherapy – Development of CO60 Teletherapy, Linear Accelerator, Mega Voltage therapy and Super Voltage therapy following 2nd World war .  In 1960s Cesium, Iridium, Palladium, Iodine in Brachytherapy were developed  Over the past 20 years , much of advances is seen in treatment planning such as 3 - dimensional treatment planning systems, IMRT etc to localize the radiation dose. www.indiandentalacademy.com
  6. 6. Radiation Physics  Radiation is transmission of energy through space and matter.  There are two types of Therapeutic Radiation:- (1)Electromagnetic radiation (photons) : X-rays, Gamma rays. (2) Particulate radiation : Electrons, Positrons, Protons, Neutrons, α particles. www.indiandentalacademy.com
  7. 7.  High energy X- rays and Gamma rays are used most often in radiation therapy  These electromagnetic radiation subtypes do not differ in any physical characteristic or in their biologic action.  The only distinction is - how they are produced and tissue penetration characteristics. Electromagnetic Radiation www.indiandentalacademy.com
  8. 8. X-rays  X-rays are created by linear accelerators (linacs). - which involve an electrical input that causes a filament to become heated and which serves as a source of electrons. - These high energy electrons are directed to hit a metal target ( made of tungsten),their by converting part of the kinetic energy of electrons to x- rays  The energy of x-rays is specified by MeV (megavolt, million volt). www.indiandentalacademy.com
  9. 9. Gamma - rays  Gamma rays are produced by materials such as radium, uranium, cobalt60  These materials undergo radioactive decay, resulting in the emission of gamma ray photons.  Because of high radiation dose and perceived radiation safety, most modern radiotherapy centers use high energy x- rays produced by linacs. www.indiandentalacademy.com
  10. 10. Particle therapy  This type of therapy differs from photon radiotherapy in that it involves the use of fast-moving subatomic particles to treat localized cancers.  Such as electrons , positrons, protons, neutrons, alpha particles, negative π mesions beams. www.indiandentalacademy.com
  11. 11. Electron Therapy  Small, negatively charged particles  These are accelerated to high energy(upto 50 MeV) by means of linacs.  A charged particle deposits uniform dose for a certain distance & then virtually none  Hence, the tissue beyond the tumor gets little irradiation  Deliver maximum dose to superficial tissues  Used in treatment of malignant lesions located at limited depths , such as BCC or metastasis to cervical LN www.indiandentalacademy.com
  12. 12. Electron Beam Therapy Machines  Kilovoltage Machines  Linear Accelerators www.indiandentalacademy.com
  13. 13. Kilovoltage Machines  Earliest X- ray machines used in treatment of cancer  Generate low energy radiates from 50 kV-100 kV  Poor penetrating quality  Used in treatment of superficial tumours www.indiandentalacademy.com
  14. 14. Linear Accelerators (linacs)  High energy X ray machines  In electron mode of linac opertion, the electon beam is directed to strike an electron scattering foil instead of tungsten target.  High penetrating power of the radiation  More effective in treatment of deep seated tumours with reduced dose of radiation  Skin sparing www.indiandentalacademy.com
  15. 15. Proton therapy  Protons are positively charged particles, its mass is 1835 times greater than electrons.  Essentially it has same radiobiologic properties such as electron or photon beam.  Because of the heavier masses - more complex and expensive equipment like cyclotron or synchrotron is needed to accelerate protons to clinically useful energies.  Because of greater flexibility of modulating protons beams to conform to target volume.  Proton therapy are used in irradiating tumors located close to critical organs ( chorodial melanomas, skull base chondromas and sarcomas) www.indiandentalacademy.com
  16. 16. Neutron beam therapy  Large, neutral particles with high linear energy transfer (LET) - thus producing denser ionization in tissues  2 major sources of neutrons: Cyclotron for External beam therapy Californium for interstitial therapy  Chief advantage of Neutrons: effective against hypoxic cells because neutrons produce much denser ionization in tissues  Used mainly for unresectable or recurrent salivary gland cancers.  Disadvantage: fast neutrons lack skin sparing and therefore can cause more acute dermal reactions compared to photons www.indiandentalacademy.com
  17. 17. Absorbed dose  Is a ratio between the average amount of energy (E) deposited in a small volume with mass(M). - Older unit of absorbed dose is Rad, which is 100 ergs of energy deposited in 1 gram of material. - Standard unit is changed to Gray(Gy), which represents 1 joule of energy deposited in kilogram of material. 1 Gy = 100 rad. www.indiandentalacademy.com
  18. 18. How Does Radiation Act ??  Absorption of the energy (electromagnetic or particulate radiation) in the body produces a minimal amount of heat, and ionizations that lead to a variety of biological effects.  The type of physical interaction depends on the energy and type of the incident photon and on the characteristics of the absorbing material.  X-ray or gamma Photons (upto 10 MV) interact with atoms through three processes (1)Compton effect, (2)Photoelectric effect, and (3)Pair production. www.indiandentalacademy.com
  19. 19.  In particle radiation - electrons entering tissues undergo either elastic or inelastic collision with electrons or atoms of the absorbing material.  The elastic interaction between the electrons cause transfer of energy and producing ionization by removing one outer electron from neutral atom.  Because the binding energy of an outer electron in most elements in tissue is small, this scattering process continues, leaving a track of ionization and biologic damage.  The elastic interaction between the electron and nucleus of the atom, the electron converts some of its energy to gamma ray photon. www.indiandentalacademy.com
  20. 20. Radiation biology  Ionization radiation delivered to cells or tissues initiates a chain of events based on energy and type of radiation.  The energy deposited is converted into secondary electrons that break chemical bonds directly or indirectly.  Direct Effect – Radiation causes a change in the molecular structure of organic compounds.  Indirect Effect - Photons interact with water producing free radicals which cause biological changeswww.indiandentalacademy.com
  21. 21.  Sparsely ionizing radiation , such as X- rays or gamma rays, induce damage mainly through Indirect effects  Densely ionizing radiation such as Neutrons & α- particles cause damage primarily through Direct effects www.indiandentalacademy.com
  22. 22. Effects On Cell Kinetics  Radiation affects the expression of cyclins and cyclin dependent kinases.  These are group of proteins which progress the cell division cycle.  This effect is most pronounced at early part of G1 phase & at the G1 to S boundary resulting in a net delay in cellular progression through division cycle.  Low dose induces mild mitotic delay  Moderate dose results in longer mitotic delay & some cell death  Larger doses may cause profound mitotic delay with incomplete recovery www.indiandentalacademy.com
  23. 23.  Although ionization radiation can affect tissue through many mechanisms, depending on the size of the dose.  Cell killing is the major effect in the therapeutic dose range.  Lethally injured cells die in 2 ways: - Mitotic (Reproductive) death - Cell death by Apoptosis www.indiandentalacademy.com
  24. 24. Mitotic (Reproductive) death  Dominant mode of cell killing in radiotherapy  Cells die when they attempt to divide.  At molecular level - Damage during late S & G2 phase- 1 arm of chr break seen- chromatid aberration or single strand breaks (SSbs) - Damage during G1 & early S phase- Both arms of chr break seen at mitosis as 1 broken arm replicates into 2 broken arms- chromosomal aberration or double strand breaks (DSBs).  These molecular events are main cause for mitotic cell death. www.indiandentalacademy.com
  25. 25. www.indiandentalacademy.com
  26. 26. Cell death by Apoptosis  Usually occurs within hours of radiation exposure.  Typically seen in after lower radiation doses.  Apoptosis is an active mode of cell death characterized by distinct biochemical and morphological features.  Which includes endonuleases activation, chromatin condensation and margination, along with cellular shrinkage and fragmentation www.indiandentalacademy.com
  27. 27. Factors affecting radiation sensitivity  Many factors affect the sensitivity of normal and malignant cells and the response of normal tissues and tumors to radiation. - i) Oxygen status - ii) Cell age in in the division cycle - iii) Type of radiation www.indiandentalacademy.com
  28. 28. Oxygen status  The ability of ionizing radiation to cause biologic change is very much dependent on the amount of oxygen present in the tissue environment.  Greater cell damage sustained in the presence of oxygen is related to increased amount of hydrogen peroxide & hydroperoxyl free radicals formed which causes DNA damage and prevents its repair,which ultimately leads to cellular death.  Oxygen is the most potent radiosensitizer .  Cells in a 100 percent oxygen environment are 3times more radiosensitive than cells in complete anoxia. www.indiandentalacademy.com
  29. 29. Cell age in in the division cycle www.indiandentalacademy.com
  30. 30. www.indiandentalacademy.com
  31. 31. Type of radiation  Different type of radiation induce different densities of ionization or energy deposition per unit length of track, called linear energy transfer (LET).  X-rays , gamma rays, electrons and protons are low LET radiation because they produce sparse density of ionization.  Neutrons and heavy nuclei produce dense ionization hence referred as high LET radiation. www.indiandentalacademy.com
  32. 32. Dose  The Radiation Therapy Oncology Group (RTOG) has conducted a dose- searching study to determine the maximum dose that could safely be given for patients with head and neck cancers. 67.2, 72, 76.8, or 81.6 Gy at 1.2-1.5 Gy given twice daily They all incorporate at least a 6-hour interval between sequential radiation treatments to allow for repair of sub lethal and potentially lethal damage in the irradiated healthy tissues. www.indiandentalacademy.com
  33. 33.  Between 66 and 70 Gy are usually prescribed for primary tumors measuring 2 cm or less.  When radiotherapy alone is delivered to a patient with more advanced disease, doses of 70 Gy or more are necessary to control the primary tumor and involved nodes.  The dose of radiation required for loco-regional control increases as tumor size increases.  Patients with lymphadenopathy of neck nodes that measure 2 cm or less - EBRT alone can control more than 90%  Nodes that measure 2 to 3 cm - doses of 70 Gy or more sterilizes only approximately 80% www.indiandentalacademy.com
  34. 34. Radiobiological Basis of Fractionation  Use of multiple fractions over many weeks of radiation therapy is based on the principle of improving the therapeutic ratio between normal tissue & tumor  The goal is to maximize the cell death of tumors and to minimize unacceptable damage to normal cells.  This can be accomplished through the use of multiple fractions and is explained by 4 radiobiologic process Conventional regimen Curative -1.8 – 2 Gy / day given amounting to 66 – 70 Gy in 33 fractions over 6 ½ weeks. Palliative - 3 Gy/day is given i.e., 30 Gy in 10 fractions over 2 weeks.www.indiandentalacademy.com
  35. 35. Radiobiological Basis of Fractionation  Repair  Re-oxygenation  Repopulation  Redistribution www.indiandentalacademy.com
  36. 36. Repair of sublethal cells  Fractionation helps in recovery of sub lethally damaged cells.  The repair capacity varies among different cells and tissues.  Repair may occur to a greater degree in slowly dividing normal tissue(late responding) compared to tumors (rapidly reacting tissues) - thus contributing to beneficial therapeutic ratio www.indiandentalacademy.com
  37. 37. Repopulation (Regeneration)  Depletion of cells (during therapy), in both normal & neoplastic tissues, triggers a regenerative response  This accelerates the - rate of cellular proliferation, results in net increase in cell production  Which is beneficial interms of reducing injury to normal tissue  But tumor with rapid cell turnover exhibit early onset of regenerative response, which reduce the likelyhood of cure. www.indiandentalacademy.com
  38. 38. Redistribution  In initially asynchronous cell population , the 1st radiation dose preferentially kills cells in sensitive phases.  Consequently cell surviving in the 1st dose tend to be partially synchronized in more resistant phases.  And these cells will resume their progression to more radiosensitive phases of cell division cycle, resulting in a net sensitization to next dose fraction.  It takes place mainly in tissues with moderate to rapid cell turn over(actually reacting normal tissues & tumors) and is negligible in late responding normal tissues. www.indiandentalacademy.com
  39. 39. Reoxygenation  Bulky tumors may have centers that relatively hypoxic due to their location away from a blood vessel  Tumor cells located in this region would be more resistant to radiation due to the low oxygen tension  During course of fractioned radiation the oxygen status of originally hypoxic cells gradually improves before subsequent doses. www.indiandentalacademy.com
  40. 40.  This process(reoxygenation) results from a number of mechanisms, such as: - the preferential elimination of more radiosensitive oxygenated cells increases oxygen availability to surviving hypoxic cells. -also lowers the interstitial pressure on micro vessels with in the tumor resulting in improved microcirculation and oxygen supply. - tumor shrinkage and active tumor cell migration bring previously hypoxic micro regions closer to blood vessels. www.indiandentalacademy.com
  41. 41. Altered Fractionation Techniques For Radiation Therapy
  42. 42.  Wilhers identified hazard of accelerated tumour clonogen repopulation during conventional once-a-day radiation therapy as one likely cause of treatment failure  4 primary fractionation factors - Dose per fraction - Total dose - Overall treatment - Treatment interval www.indiandentalacademy.com
  43. 43. Altered fractionation stratergies A) Hyperfractionation - Decreased fraction size - Increased fraction number - Increased total dose - Maintain overall treatment time - Rationale : Allows safe delivery of high tumors dose without increase in late normal tissue toxicity www.indiandentalacademy.com
  44. 44.  Strategy of Hyperfractionation is to use an increased no. of smaller doses per fraction than conventional 1.8 - 2.0 Gy per day 1.2 to 1.5 Gy twice daily to a total dose of 80.5 Gy over 7 weeks.  This is associated with increase in acute complications and reduction in the late complication www.indiandentalacademy.com
  45. 45. B) Acceleration Fractionation  Decrease in overall treatment time - Maintain or slightly reduce - Fraction size - Fraction number - Total dose  Accelerated fractionations attempt to reduce tumor proliferation, which is the major cause of RT failure.  Rationale: Counteract adverse effects of tumor cells repopulation by decreasing over all treatment time. www.indiandentalacademy.com
  46. 46. Newer Regime Continous Hyper Fractionated Accelerated Radiation Therapy (CHART) 54 Gy in 36 fractions – 1.5 Gy T.I.D. over 12 consecutive days. www.indiandentalacademy.com
  47. 47. www.indiandentalacademy.com
  48. 48. Indications for Radiotherapy
  49. 49. Indications for Radiotherapy  T1-T2 lesions  T3,T4 Locally advanced lesions - Post surgical treatment - Only therapy if surgery not possible  Cervical lymph node Pre-surgical & post surgical in combination with neck dissection for clinically positive lymph nodes. www.indiandentalacademy.com
  50. 50. General Concept Of Radiotherapeutic Techniques
  51. 51. Treatment planning  Radiation treatment plan is based on tumor site, tumor size, the total volume to be radiated , the number of treatment fractions, total number of days of treatment, and tolerance of patients.  Also includes planning for sparing of uninvolved tissues or organs. www.indiandentalacademy.com
  52. 52. Patient positioning & Immobilization  Radiotherapy can be delivered in supine, prone or even sitting position  Immobilization, accuracy & reproducibility are better achieved in supine or prone position  Immobilization is essential as high dose must be given accurately to a small volume avoiding adjacent vital radiosensitive structures.  Head holders , bandages ,laser positioning, head and neck “landmarks” or tattoos and custom acrylic shells are used for positioning and immobilization.  Thin transparent plastic shell is moulded to patient’s skin to mark the field size, entry & exit points. www.indiandentalacademy.com
  53. 53. Patient positioning and immobilization devices are used to achieve true reproducibility and accuracy in set up. Head Frame With Bite Block www.indiandentalacademy.com
  54. 54. Simulation & Beam verification  Simulator is an isocentrically mounted diagnostic X-ray unit that mimics geometrical arrangement of radiotherapy machine.  The aim of simulation is to accurately target or localize the volume which is to be treated  A patient is placed on the couch in treatment position & field are aligned  Alignment is done either clinically or with Flouroscopic screening facility  Tumor volume is localized & verification X ray is taken  Lead blocks and shields made to ensure that radiation reaches only the target tissue.www.indiandentalacademy.com
  55. 55. Techniques of Radiotherapy
  56. 56. Clinical Radiotherapy Techniques Brachytherapy Teletherapy www.indiandentalacademy.com
  57. 57. Brachytherapy  Brachio in greek means short range  Brachytherapy is the sub specialty of radiation oncology which uses selected Radioisotopes and specialized instruments to directly administer radiation to tumor bed www.indiandentalacademy.com
  58. 58.  Two types of implants: Removable Implants: Radium, Tantalum, I 125 & Ir 192 & Co60 Permanent Implants: (left insitu to decay completely) Gold grains & Radon seeds  Brachytherapy radiation travels only a short distance to the desired target region without effecting surrounding normal tissues - Its dose intensity has a rapid fall off with distance according to the inverse square law [I~ 1/ D2] This causes sharp ↓ in dosage in surrounding tissues The dose rate can be low and continuous LDR - 40 to 200 cGy / hr HDR – 1200 cGy / hrwww.indiandentalacademy.com
  59. 59. Here radioactive sources are implanted into the tumor for definite period (temporary implants) or indefinitely (permanent). The source can be in the form of needles, wires, and seeds. Used in management of squamous cell carcinoma of Head and Neck, skin, breast tumor, soft tissue sarcoma and many others. www.indiandentalacademy.com
  60. 60. Intracavitary brachytherapy  Treatment by placement of radioactive sources inside natural body cavities.  Mainly used in gynecological malignancies. www.indiandentalacademy.com
  61. 61. Advantages:  Ideally suited for anatomical locations where tumor is well localised to tissues (Anterior part of tongue)  High doses of radiation delivered in & near the tumor Disadvantages:  GA is necessary for insertion of these sources  Increased radiation exposure to radiation personnel  Treated volume is small www.indiandentalacademy.com
  62. 62. Dose:  Typically, about 3.0 to 3.5 Gy is given to a distance of about 1 cm ( from the periphery of the catheters), and two daily treatments are given about 6 hours apart. Each treatment takes about 15 to 30 minutes Precautions for Brachytherapy:  Patient -nurse contact is kept to the minimum  Patient remains in the ward for up to seven days  Patient is sedated before plastic tubes are removed www.indiandentalacademy.com
  63. 63. Radioactive Isotopes  Systemic radiation in which isotopes are injected IV  Useful therapeutic effects can be obtained if the target organ concentrates the isotopes & increases the specific dose  Systemic radiation therapy is sometimes used to treat cancer of the thyroid(I131 ), polycythemia Vera(P32 )and adult non-Hodgkin's lymphoma.  Ideal requisites of a radiopharmaceutical for RT i. Effective half-life should be in hours to days. ii. Medium/high energy (>1 MeV). iii. Minimal radiation dose to patient and Nuclear Medicine personnel iv. Patient Safety v. Should be readily available www.indiandentalacademy.com
  64. 64. Teletherapy (External beam thearpy)  “Tele” means far or distant  Here beam comes from a source located at a distance from the patient and directed towards the patient.  External beam therapy can be broadly divide into two types based on beam quality and their use.  Kilovoltage therapy - Megavoltage therapy Kilovoltage is further divided into 3 types i) Contact therapy ii) Superficial therapy iii) Orthovoltage or deep therapy www.indiandentalacademy.com
  65. 65. Contact therapy  Contact therapy operates at potentials of 40-50 kV and tube current of 2mA.  Facilitates irradiation of accessible lesions from very short source to surface distance(SSD) i.e 2 cm or less  Because of very short (SSD) and low voltage, the contact beam produces a very rapidly decreasing depth dose in tissue hence skin surface is maximally irradiated but the underlying tissues spared.  Useful for tumors less than 1 -2 mm in thickness. www.indiandentalacademy.com
  66. 66. Superficial therapy  Term superficial therapy applies to treatment with x-rays produced at a energy ranging from 50 to 150 kV and tube current of 5-8mA .  SSD ranges from 15 cm to 20 cms .  Is useful for irradiating tumors confined to about 5mm.  Beyond this, the dose fall off is too sharp to deliver adequate dose. www.indiandentalacademy.com
  67. 67. Orthovoltage or deep therapy  Term orthovoltage therapy is used to describe treatment with x-rays ranging from 150 – 500 kV. At a tube current of 10 to 20 mA.  SSD is approximately 50cms.  The maximum dose is delivered close to the skin surface, with 90% isodose value occurring value occurring at a depth of about 2cms.  Disadvantage – Higher skin dose  Increased scatter  Greater bone absorption – leading to beam energies unsuitable for treatment for the treatment of tumors behind the bone. www.indiandentalacademy.com
  68. 68. Megavoltage therapy  X-ray beams of energy 1 MV or greater can be classified as megavoltage beams  The term strictly applies to the X-ray beams, the gamma- ray beams of energy 1 MeV or greater.  Examples for clinical megavoltage machines are Van de Graaff generator, linear accelerator, betatron, microtron and telecobalt units www.indiandentalacademy.com
  69. 69. The Radiotherapeutic Techniques  Single field arrangement  Parallel opposed fields  Wedge lateral field  Multiple fields  Rotational & Arc therapy www.indiandentalacademy.com
  70. 70. Single Field Arrangement  Tumor is treated with one field only  Quick & easily reproducible therapy Parallel opposed fields  Two parallel fields are opposite to one another  Produces fairly even distribution through out the irradiated area www.indiandentalacademy.com
  71. 71. Radiation fields Lateral field Antero Posterior Field www.indiandentalacademy.com
  72. 72. Wedge lateral field  Two right angled fields can be combined to irradiate a discrete tumor volume rather than placing them parallel. Multiple fields  Most common form is with 4 fields arranged 2 parallel & 2 opposed pairs (4 Field Brick technique) produces good tumor localization www.indiandentalacademy.com
  73. 73.  Moving field techniques which are modifications of multiple field therapy  Radiation source rotates around the tumor isocentrically  To provide an even dose through out the tumor volume  To spare a selected normal tissue from the primary beam, only a part of rotation ( Arc therapy) is made Rotational & Arc therapy www.indiandentalacademy.com
  74. 74. Methods to Reduce Side Effects:  Collimation/filtration  Fractionation of dose  Use of high LET radiation  Chemical radio sensitizers  Hyperbaric oxygen www.indiandentalacademy.com
  75. 75. Combined Therapy: Multimodality Therapy
  76. 76. Preoperative Radiotherapy Advantages:  Eradicate subclinical disease beyond resection margins  Prevention of marginal recurrences  Prevention of implantation of tumor cells at surgery  Control of subclinical disease at 1º site & in LN www.indiandentalacademy.com
  77. 77.  Dosage  180 to 200 cGy/ fraction 1 fraction/day ;5 days/ wk, to a total dosage of 5,000 to 6,000 cGy After completion of treatment - 4 to 6 wk gap prior to surgery  To allow for patient recovery,  To decrease acute inflammatory reaction  To allow for a maximum clinical shrinkage of tumor www.indiandentalacademy.com
  78. 78. Disadvantages  Diminished wound healing  Delay of definitive surgery  Can’t cure already developed occult distant metastasis  Increased cost  Combined therapy is unnecessary for early lesion www.indiandentalacademy.com
  79. 79. Post operative Radiotherapy  Indications - When estimated risk of loco regional recurrence is > 20 % - Advanced T3 or T4 lesions - Positive or close margins of resection - Perineural/vascular invasion - High-grade histology www.indiandentalacademy.com
  80. 80. Drawbacks of Post operative Radiotherapy - Delay in initiation of radiation therapy due to wound complications from surgery - Scarring & vascular modifications from surgery may decrease tissue oxygenation- adversely affects radiation tumor cell kill www.indiandentalacademy.com
  81. 81. Concomitant Chemoradiotherapy  Unresectable disease to improve local & regional control  Mechanism for interaction b/w cytotoxic drugs & radiation that results in additive or synergistic phenomenon rests on several mechanisms - Inhibition of DNA repair - Redistribution of cells in sensitive phases of the cell cycle - Promoting oxygenation of anoxic tissues  The net effect is to improve cellular cytotoxicity  Specific chemotherapeutic drugs such as fluorouracil, cisplatin, and taxanes induce cell cycle arrest at the G2 checkpoint, where the cell is most radiosensitive www.indiandentalacademy.com
  82. 82. Multiple Agents & Radiotherapy  Improved survival time- primary goal  Combining several drugs with radiation- Acute toxicity- trials designed with split course radiation- allow healthy tissue recovery  Infusional 5-FU + cisplatin or Hydroxyurea + concurrent split-course single daily fraction radiation- promising survival and response data but also severe toxicity www.indiandentalacademy.com
  83. 83. Advances in Radiotherapy
  84. 84. Modification Of Tumor Hypoxia  Cellular Hypoxia is considered as an important factor in control of head & neck cancer  Methods to increase tumor oxygenation: - Hyperbaric oxygen - Oxygen mimetic hypoxic cell sensitizers - Modified Radiation Fractionation www.indiandentalacademy.com
  85. 85. Hyperbaric oxygen therapy  Oxygen under high pressure is given to the patient  Usually given as 20-30 dives at 100% oxygen & 2-2.5 atm pressure  Increases oxygenation of irradiated tissue  Promotes Angiogenesis  Enhances osteoblast repopulation www.indiandentalacademy.com
  86. 86. Hypoxic Cell Sensitizers  Group of Bioreductive Nitroimidazole drugs which mimic oxygen  Selectively Radiosensitised hypoxic cells  Misonidazole & Etanidazole  Side effect: Neurotoxicity  Nimorazole- decreased toxicity & well tolerated www.indiandentalacademy.com
  87. 87. Tirapazamine  New bioreductive agent  Undergo selective electron reduction in hypoxic conditions, forming free radicals, which result in cell death  Potentiates the cytotoxicity of ionizing radiation & several chemotherapeutic drugs  Nicotinamide, which causes vasodilation – reduces transient or acute hypoxia www.indiandentalacademy.com
  88. 88. Radio protectors  Amifistone (Ethyol)- sulfhydryl compound that acts as potent scavenger of free radicals generated in tissues exposed to radiation  Approved by the US FDA for management of RT- induced salivary dysfunction  The sulfhydryl compound, WR- 2721 selectively protected the normal tissues against effects of radiation. www.indiandentalacademy.com
  89. 89. Conventional external beam radiotherapy  Conventional external beam radiotherapy (2DXRT) is delivered via two- dimensional beams ( height and width) using linear accelerator machines.  2DXRT mainly consists of a single beam of radiation delivered to the patient from several directions: often front or back, and both sides.  2DXRT are planned by using a specially calibrated diagnostic x-ray machine known as a simulator because it recreates the linear accelerator action.  This technique is well established and is generally quick and reliable. www.indiandentalacademy.com
  90. 90. Conformal Radiotherapy  Conformal radiotherapy is also called 3D conformal radiotherapy (3DCRT).  It uses a special way of planning and giving radiotherapy.  In conformal RT the image of the tumours obtained in three dimensions (3D);width, height and depth, using CT scan or MRI Scan,PET.  The information from these scans feeds directly into the radiotherapy planning computer.  Then the computer programme the designs radiation beams that ‘conform’ more closely to the shape of the tumour and avoid healthy tissue as far as possible. www.indiandentalacademy.com
  91. 91. Intensity Modulated Radiotherapy  Like conformal radiotherapy, IMRT shapes the radiation beams to closely fit the area where the cancer is.  And also alters the radiotherapy dose depending on the shape of the tumour - Using radiation beams of varying intensity (beamlets), - i.e the central part of the cancer receives the highest dose of radiotherapy and a surrounding area of tissue gets lower doses.  IMRT is ideally suited for H & N malignancies, if there is proximity of the tumor to the critical structures. www.indiandentalacademy.com
  92. 92.  IMRT is done with Linear accelerator (LINAC) with multi-leaf collimator that moves around the patient and shapes the beams of radiotherapy to fit the tumour. www.indiandentalacademy.com
  93. 93. Image-guided radiation therapy (IGRT)  Traditionally, imaging technology has been used to produce three- dimensional scans of the patient’s anatomy to identify the exact location of the cancer tumor prior to treatment.  However, difficulty arises when trying to administer the radiation, since cancer tumors are constantly moving within the body (for example, from movement caused by breathing or tumor shrinkage).  Hence, the exact location of the tumor may have changed between the time of scan and actual treatment and fractionation. www.indiandentalacademy.com
  94. 94.  IGRT combines scanning and radiation equipment, - i.e IGRT uses a linear accelerator (IMRT), equipped with a kilovoltage imaging source and solid state X-ray detector (X-ray Volume Imaging).  This enables physicians to adjust the radiation beam based on the position of the target tumor and critical organs, while the patient is in the treatment position.  Thus IGRT reduce the exposure of healthy tissue during radiation treatments. www.indiandentalacademy.com
  95. 95. Hyperthermia & Radiation Therapy  Supra normal temperature in the range of 41-430 C sensitizes cells to radiation.  It selectively injures 2 kinds of cells that are most resistant to irradiation: Hypoxic cells & cells in late S phase of cell cycle Greater Hyperthermia occurs in cancer cells because:  Sluggish heat dissipation by tumor blood flow  Heat makes micro environment in tumor more acidic & nutritionally deprived  Radiofrequency, Microwaves, Ultrasound  Giving heat 1-5hrs after irradiation can attain max. therapeutic gain www.indiandentalacademy.com
  96. 96. Radioimmunotherapy  Use of radio labeled antibodies to deliver doses of radiation directly to the cancer site  Antibodies are highly specific proteins that are made by the body in response to the presence of antigens (substances recognized as foreign by the immune system).  Some tumor cells contain specific antigens that trigger the body's immune system to produce tumor-specific antibodies.  Large quantities of these antibodies can be made in the laboratory and attached to radioactive substances (a process known as radiolabeling). www.indiandentalacademy.com
  97. 97.  Once injected into the body, the antibodies actively seek out the cancer cells, which are destroyed by the cell-killing (cytotoxic) action of the radiation.  The benefit to this approach is that it can minimize the risk of radiation damage to the body's healthy cells.  The success of this technique will depend upon both the identification of appropriate radioactive substances and determination of the safe and effective dose of radiation that can be delivered in this way. www.indiandentalacademy.com
  98. 98. TREATMENT OF RECCURENCE  90% of the recurrence occurs within 2 years.  8% of recurrence occurs after 5 years. In such cases debulking or radical surgery should be attempted.  Reirradiation will be helpful only after one year.  50-65 Gy Hyper fractionation / Brachytherapy are used to improve the tolerance of tissues to radiotherapy. www.indiandentalacademy.com
  99. 99. THE ROLE OF RADIATION THERAPY ALONE FOR HEAD AND NECK TUMOR - BY SITE
  100. 100. Lip  T1 to T2 lip cancers - Surgery / radiation therapy can be considered for primary treatment of based on specific anatomic location and size of the lesion.  Radiation therapy is indicated for: - Commissure involvement, - Patients who refuse surgery, and superficial lip cancers involving less than one-third of the entire lip. - Small lesions are treated with interstitial implant alone. - Larger lesions may require external beam radiation therapy with an interstitial boost. www.indiandentalacademy.com
  101. 101. Oral cavity  For early T1 & T2 lesions - radiation therapy & surgery are equally effective in achieving local control.  Superficial lesions that are ≤ 2 cm (T1), away from the bone – can be treated with interstitial implant alone.  Lesions > 2 cm and ≤ 4 cm (T2) - without clinical lymphadenopathy can be treated with external radiation therapy (5,000 cGy) - with adjacent regional lymph nodes involvement - external radiation therapy (5,000 cGy) + temporary interstitiary implant (2,000 to 2,500 cGy). www.indiandentalacademy.com
  102. 102.  For moderately advanced T2 to T3 lesions, full course external beam radiation therapy is used.  For lesions in the floor of mouth and tongue, extension of disease deep into the musculature and into adjacent mandibular bone would best be treated with surgery and postoperative radiation therapy. www.indiandentalacademy.com
  103. 103. Floor of Mouth  T1 & T2 lesions can be treated - surgery / radiation therapy.  T1 & T2 lesions + clinically positive nodes - surgical resection of the primary lesion and a neck dissection .  Postoperative external beam radiation therapy is indicated for close or positive margins in the primary site and/or nodal disease.  Post operative radiation is to be given, within 6 weeks after surgery to a dosage of 6,300 cGy to the primary site and high-risk node.  An early lesion extends to the ventral aspect of the tongue - radiation therapy is preferred to avoid functional morbidity. www.indiandentalacademy.com
  104. 104. Tongue  T1 and T2 lesions can be treated with surgery / radiation therapy.  Primary radiation therapy - dosage of 4,000 cGy of external beam irradiation to tongue and regional nodes - with a subsequent brachytherapy boost of 3,000 cGy. 5,000 to 5,400 cGy is administered for elective nodal irradiation.  Advanced T3 & T4 lesions are generally approached with surgery and postoperative radiation therapy within 6 weeks of the procedure. www.indiandentalacademy.com
  105. 105. Base of Tongue  T1 and T2 lesions can be successfully treated by either surgery or radiation therapy.  Majority of patients are usually treated with radiation therapy, as it provides a better functional outcome and quality of life with equivalent control rates.  Patients with T1 and T2 lesions - conventional fractionation of primary lesion upto 5,400 cGy, the involved neck nodes to 6,000 cGy and elective nodal irradiation to 5,000 to 5,400cGy . www.indiandentalacademy.com
  106. 106. • Following a 3-week break - iridium 192 temporary interstitiary implant ionto the base of the tongue delivering 2,400 to 3,000 cGy. • Advanced T3 and T4 lesions often would require surgery with a partial or total glossectomy, and neck dissection to be followed by postoperative radiation therapy. www.indiandentalacademy.com
  107. 107. Salivary glands  Surgery is the treatment of choice for both primary and locally recurrent salivary gland tumors.  For unresectable primary or recurrent lesions, the use of neutrons is indicated.  Postoperative radiation therapy is an important part of treatment and is indicated: (1) resectable primary T4 and recurrent tumors, (2) high grade lesions, (3) positive or close margins, (4) perineural/vascular invasion (5) locoregional lymph node metastasis. www.indiandentalacademy.com
  108. 108.  Dosage: 6 MV x-rays are administered,  If the treatment is postoperative, 180 cGy per fraction is given to a total dosage at 6,300 cGy to the primary area and high risk lymph node levels.  5,000 to 5,400 cGy is administered for elective nodal irradiation when indicated www.indiandentalacademy.com
  109. 109. Pre Irradiation Dental Care  Extraction of unrestorable teeth & those with advanced periodontal disease  Extractions done14-21 days prior to radiation therapy  Antibiotic use  Fluoride (neutral sodium fluoride 1%) application  Oral prophylaxis  Restore large caries  Remove partially erupted third molars, may leave full bony impacted teeth if surgical difficulty. www.indiandentalacademy.com
  110. 110. Post-treatment Protocol  Regular application of fluorides & regular check up  Salivary substitutes for salivary dysfunction  Proper nutrition - especially proteinaceous food  Post treatment follows up at regular intervals  Counseling and group therapy and other methods for proper emotional adaptation of the patient.  Avoidance of all surgical procedures involving bone for a minimum of six months www.indiandentalacademy.com
  111. 111. Complication of Radiotherapy
  112. 112.  Under 3,000 cGy — Mucositis, candidiasis, xerostomia & dysgeusia begin  Over 3,000 cGy - xerostomia (permanent) and taste dysgeusia , altered saliva (thick, more acid, changed flora)  Over 5,000 cGy - Trismus - concerns for osteoradionecrosis  Over 6,000-6,500 cGy significant concern for osteoradionecrosis  Stimulated Whole Salivary Flow Rates - 57% decrease in a week after beginning of RT & after 5 weeks (end of treatment) 76% decrease..  Endocrine abnormalities: Hypothyroidism, Parathyroid adenoma and hyperthyroidism.  Atherosclerosis occurs in doses more than 50 Gy www.indiandentalacademy.com
  113. 113.  Progressive muscle fibrosis may limit the neck and shoulder function. Some times trismus may also seen.  Visual impairment may occur due to radiation keratitis, cataract and optic neuritis.  Radiation neuritis.  Secondary infection.  Development of maxillofacial deformity and defective tooth development in children. www.indiandentalacademy.com
  114. 114. Sequelae of radiation therapy ORN Oral candidiasis Xerostomia Soft tissue fibrosis Trismus Obliterative endartritis Slow/ non healing ulcerswww.indiandentalacademy.com
  115. 115. Mucositis  The oral mucous membrane consists of Basal layer composed of radiosensitive vegetative & differentiating intermitotic cells  Near the end of 2nd week of therapy, as some cells die, mucous membrane begins to show some areas of redness & inflammation – Mucositis  The irradiated mucous membrane begins to break down, with the formation of white to yellow pseudo membrane www.indiandentalacademy.com
  116. 116.  After irradiation is completed, mucosa begins to heal rapidly  Healing is complete by about 2 months  After months to yrs, mucous membrane tends to become atrophic, thin & avascular  This long term atrophy results from progressive obliteration of fine vasculature Fibrosis of underlying connective tissue www.indiandentalacademy.com
  117. 117. Clinical features  The early clinical sign of mucositis is Erythema presenting about 4–5 days following cumulative doses of head and neck radiation of about10 Gy.  Patients also often complain of burning and intolerance of spicy foods  Seven to 10 days after chemotherapy or at cumulative radiation doses of 30 Gy, ulcers develop, resulting in marked discomfort www.indiandentalacademy.com
  118. 118. Management Of Mucositis Oral care & Topical therapy:  Bland oral rinses & topical anesthetics  Saline, Bicarbonate  Lubricating jelly  Milk of magnesia  Benzydamine HCl  Sucralfate suspension  Povidone-iodine rinses www.indiandentalacademy.com
  119. 119. Management Of Mucositis Methods to reduce exposure of the mucosa to damaging agents  Ice chips  Propantheline Antimicrobials  Aciclovir  Antibiotics  Amphotericin B  Chlorhexidine  Fluconazole www.indiandentalacademy.com
  120. 120. Anti-inflammatory medications Biologic response modifiers  Interleukin-1,11  GM-CSF  G-CSF  Keratinocyte growth factors www.indiandentalacademy.com
  121. 121. Cytoprotective agents  Amifostine  Benzydamine  Glutamine  N-acetyl cysteine  Prostaglandins  Vitamin E Low-energy lasers www.indiandentalacademy.com
  122. 122. Oral candidiasis • A fair number of patients will develop an oral Candida infection . • May be asymptomatic / may complain of an acute development or exacerbation of their sore mouth or throat. •Initiation of antifungal medication will usually resolve the problem. www.indiandentalacademy.com
  123. 123. Taste buds  Extensive degeneration of normal histological architecture of taste buds  Hypoguesia, Aguesia & Dysguesia  Taste loss may begin with radiation dose of 20 Gy  Returns to normal in about 1 yr after RT  Zn sulfate 220 mg, twice daily – recovery of taste disturbances www.indiandentalacademy.com
  124. 124. Salivary glands  Parenchymal component is radiosensitive  Extent of reduced salivary flow is dose dependent  Reaches zero at 60 Gy  Mouth becomes dry (Xerostomia), tender, dysphagia  Swallowing becomes painful & difficult  Small volume of viscous saliva has Ph of 5.5  Buffering capacity decreases by 44%  Alteration of micro flora ( Acidogenic)  Increased Streptococcus mutans, Lactobacillus & candida www.indiandentalacademy.com
  125. 125. Management of Xerostomia  Preventive therapy ( Topical Fluorides , Regular dental visits )  Symptomatic treatment (sipping water frequently , room humidifiers, oral rinses & gels, Artificial saliva)  Salivary stimulation Topical Systemic www.indiandentalacademy.com
  126. 126. SIALOGOGUES Mechanical stimulants  Eating foods which require Mastication  Artificial Sweeteners Chemical stimulants  Mucopolysaccharide solutions containing Citric Acid Electrical stimulants (TENS) www.indiandentalacademy.com
  127. 127. Proposed Systemic Sialogogues  Pilocarpine  Cevimeline  Bethanechol  Anetholetrithione  Guaifensin  Bromhexine  Neostigmine  Yohimbine  Potassium iodide  Nicotinic acid  Malic acid  Vit A www.indiandentalacademy.com
  128. 128. Radiation caries  Rampant from of dental caries  Due to exposure of salivary glands to therapeutic irradiation  Reduced salivary flow, Ph & buffering capacity  Increased viscosity of saliva www.indiandentalacademy.com
  129. 129. Clinically 3 types are present:  Widespread superficial lesions attacking all surfaces  Involving primarily cementum & dentin in cervical region  Dark pigmentation of entire crown Management:  Daily application of 1% neutral NaF gel for 5 min in custom made applicator trays www.indiandentalacademy.com
  130. 130. Radiation caries
  131. 131. Osteoradionecrosis  Primary damage to mature bone results from radiation induced damage to vasculature of periosteum & cortical bone, which are normally already sparse  Normal marrow replaced with fatty marrow & fibrous C.T  Chronic non healing wound caused by Hypoxia, Hypocellularity & Hypovascularity of irradiated tissue  Destruction of osteoblasts & osteocytes  Mandible is more commonly affected www.indiandentalacademy.com
  132. 132. Pathogenesis Therapeutic irradiation Endothelial death, thrombosis, hyalinization of BV Progressive obliterative endarteritis Decreased microcirculation Ischemia & decrease in viable osteocytes  Higher incidence of ORN when teeth are removed after radiotherapy www.indiandentalacademy.com
  133. 133. Clinical features  Severe, deep, boring pain for weeks to months  Soft tissue abscesses  Persistently draining sinus  Exposed bone with intra or extra oral fistulae  Trismus  Fetid odour  Pathological fracture www.indiandentalacademy.com
  134. 134. Therapeutic Modalities To Decrease Incidence Of ORN  Dose fractionation  Use of megavoltage  Meticulous collimation  shielding of normal tissues  Maintenance of pre irradiation & post irradiation dental health www.indiandentalacademy.com
  135. 135. Management  Debridement  Antibiotics to control secondary infection  Hydration, fluid therapy  Narcotics  Sequestrectomy & repeated irrigation  HBO therapy  Antioxidant supplements  Reconstruction of pathological fracture www.indiandentalacademy.com
  136. 136. Reference  Text book of Radiation Oncology – Principles and Practice Goura K Rath, Bindhu K Mohanti  Text of Oral Medicine Burkits  Cancer – Principle and Practice Unicent T. Devita, Samuel Hellman  Head And Neck – Surgery and Oncology Jatin Shah  Cancer of Head And Neck – Eugene N .Myer’s, James Y. Suen  Oxford hand book of Oncology Jim Cassidy, Donald Bisselt  Internetwww.indiandentalacademy.com
  137. 137. www.indiandentalacademy.com
  138. 138. www.indiandentalacademy.com

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