Practical tips to deliver spine SBRT

1. Education
Clinical Care
Research
Spine SBRT 101 : practical tips
3rd International SBRT symposium
2016
Dr. Bala Vellayappan
Assoc. Consultant
MBBS (Singapore), GDFM,
FRANZCR

2. Outline
• Background and rationale
• Determining eligibility (Patient selection)
• Required imaging
• Simulation
• Targeting
• Planning, dose selection
• OAR tolerances
• Plan evaluation
• Delivery and IGRT
• Case studies

3. Background
• Exponential rise in the use of SBRT
• Patients are living longer due to more effective
systemic therapy, and therefore durable control
becomes important
• There is a dose-response curve in palliation. Higher
doses  more durable pain relief
• SBRT affords high doses in short schedules (win-
win)

4. Rationale
• Advances in techniques, equipment and positional
verification high doses in tight spaces
• 35Gy/ 5# = BED 60Gy
• 24Gy/2# = BED 53Gy
• Large dose fractions = immune-mediated cell-killing
and endothelial apoptosis 1,2
1. Radiobiological mechanisms of stereotactic body radiation therapy and stereotactic radiation surgery.
Kim et al Radiat Oncol J. 2015 Dec; 33,265
2. Radiation-Induced Vascular Damage in Tumors: Implications of Vascular Damage in Ablative
Hypofractionated Radiotherapy. Park et al. Radiation Research: March 2012, (177),311

5. Patient Selection
• Patient factors
• KPS >50 (preferably 70)
• Life expectancy > 6m
• Able to lie still for treatment
• Not radiosensitive histology
like MM or lymphoma
• Patients with previous EBRT
<45Gy (3 months apart)
• Tumour factors
• <=3 contiguous segments
• Not in cord/cauda
compression (ideal >2mm
gap)
• Spine not unstable (SINS
score)

6. Revised Tokuhashi Score SINS score
Category Options
General Condition
(Performance status)
Poor
Moderate
Good
Number of extraspinal
bone met
>=3
1-2
0
Number of mets in
vertebral body
>=3
2
1
Mets to major internal
organs
Unremovable
Removable
No mets
Primary cancer site
Palsy Complete (Frankel
A,B)
Incomplete (Frankel
C,D)
None (Frankel E)
0-8 : 6m
9-11 : 6 – 12m
12-15 >1 y
Ref : Tokuhashi Y, et al. Spine 2005 2186-91
Component Options
Location Junctional
Mobile Spine
Semi-rigid
Rigid
Pain Yes
Occasional pain but not mechanical
Pain-free lesion
Bone Lesion Lytic
Mixed
Blastic
Radiographic spinal
alignment
Subluxation/translation present
De novo deformity
Normal
Vertebral body
collapse
>50%
<50%
No collapse with >50% body
involved
None
Posterolateral
involvement of spinal
elements
Bilateral
Unilateral
None
0-6 : stable
7 – 12: potentially unstable
13 – 18 : unstable
Ref: Fisher et al Spine 2010 1221

7. Denis’ three column concept
• One column injury is stable
• Two column injury is unstable
• Three column injury is
invariably unstable
Spinal instability as defined by the three-column spine concept in acute spinal trauma. Clin Orthop Relat Res. 1984
Oct;(189):65-76.

8. All cord compressions are not equal…
Bilsky et al J Neurosurg: Spine V13 2010

9. MSKCC NOMS algorithm
• NEUROLOGICAL ASSESSMENT
• ONCOLOGICAL ASSESSMENT
• MECHANICAL ASSESSMENT
• SYSTEMIC ASSESSMENT
Laufer et al. The Oncologist 2013; 18 : 744

10. Post-operative cases
• For patients in cord compression, or with unstable spines – upfront
surgical stabilization is preferred
• Challenges with post-operative SBRT
– Uncertainties in targeting due to streak artefacts
– Beam attenuation by rods (uncertainties in dose calculation, beam
modelling)
• Potential solutions
– Speak to your radiologist!
– Artefact reduction protocols are available
– CT myelogram delineates cord well, but may still have streak artefacts

12. Which machine should I use?

13. Is there one machine that is better?
ASTRO 2016

14. VMAT

15. Cyberknife

16. Tomotherapy – fixed jaw

17. Tomotherapy – dynamic jaws

18. You have decided to
deliver SBRT..now
what?

19. Patient preparation
• During consult –
discuss goals and
challenges of the
procedure with the
patient
• Assess pain score,
anxiety and
claustrophobia
• MRI whole spine with
contrast
– T1/T2 sag and axial
– Short tau inversion
recovery (STIR)
• Re-staging CT
• Targeted MRI (limited
sequences for RT
planning)
• +- CT myelogram
Required imaging

20. CT-Simulation
• Near-rigid immobilization
• Thick thermoplastic shell for lesions above T4 (5 point)
• BODYFix for other sites (not simple Vaclock)
• IV contrast optional (good to have)
• We don’t use 4DCT or fiducials
• <3mm cuts through region of interest
• Patient must be relaxed and pain-free *
• Recent MRI for fusion
• Good practice point : reposition patient before simulation

21. Rigid immobilisation
• T-shaped bags – more support
under the arms
• Full length bag - more support
for pelvis and legs

22. Targeting
• GTV (tumour alone) – use diagnostic MRI(T1c,T2) and PET to help
• Involve the surgeon for post—op cases
• CTV = extend GTV to cover adjacent normal looking marrow. (refer to
consensus guidelines)
• Organs at risk (at least 5cm above and below PTV)
 Cord or cauda (Defined on T2-MRI) , well above and below target
 If cord not visible, can delineate thecal sac
 Nerve root/plexus
 Esophagus PRV
 Bowel
 Kidney
 Skin (5mm)

23. Anatomy of the spine

24. RTOG 0631 targeting

25. Consensus
Cox et al Red Journal Vol 83 e597

26. What to include as CTV

27. Treatment planning
• Core group
• Dose selection
– 3 to 5 fraction SBRT is more forgiving, and still gives good results
– 24 – 27Gy in 3 fractions, 30 to 35Gy in 4 to 5 fractions
• Dose constraints
– TG 101
– RTOG 0631
– Follow what the experts do
• VMAT 2 arc
– Quicker than 9-13 field IMRT
– Non-coplanar usually doesn’t add much, and runs the risk of couch
collision
• Plan evaluation
– Know where to compromise
– Cord takes priority  there will be dose spillage outside target

28. Treatment delivery
• Equipment
– Commissioning and QA is very important
– Daily machine and indv. patient QA
• Manage the situation
– Setup, imaging, verification and delivery done swiftly
• Setup with lasers and DRO shift initially
• 3D Cone-beam CT
– Estimated to be 2-5minutes
• Tolerances should align with PTV/PRV margins (Desired 1mm/2degree)
• What to match?
• Treatment time
• Mid-CBCT ? Post CBCT?
• Pre-meds
– Dexamethasone 4mg prior to each fraction and few days after
– Adequate analgesia
– Anxiolytics as needed

29. Case study 1 (Patient 001)
• 70 Male, ECOG 0
• Metastatic Cholangioca since 2006
• Progressive C2 lesion causing neck pain
 1) Review the images
 2) Target the lesion

33. Case study 2 (Patient 003)
• 37 F, ECOG 0
• Met cervical Ca
• On PDL1 clinical trial
• Symptomatic L1 met s/p stabilisation
• For post-op SBRT
 1) Review the images
 2) Target the lesion
*Post-op targeting is more subjective. Post-op consensus guidelines likely to
be out in Red Journal soon

38. Case study 3 (Patient 009)
• 44, Female, ECOG 1
• RCC diagnosed 2007. Metastatic recurrence in 2012
• Prior RT to prevascular LN 50Gy/20# (2012)
• Started on Pazopanib, then everolimus
• Recent MRI spine shows met involving T3 and L1 vertebral body, with
involvement of superior endplate (L1)
 1) Review the images
 2) Target the lesion

40. T3 lesion

41. L1 lesion

43. Education
Clinical Care
Research
Thank you for your attention!
Email :
bala_vellayappan@nuhs.edu.sg