ROSE CASE - STEREOTACTIC RADIOTHERAPY FOR VESTIBULAR SCHWANNOMA

1. ROSE CASE
STEREOTAXY FOR VESTIBULAR SCHWANNOMA
RADIATION ONCOLOGY
SIMULATION TO EXECUTION
DR KANHU CHARAN PATRO

2. HISTORY
• 40 year male
• Diagnosed case of vestibular schwannoma
• Right side
• P/w – Tinnitus – 6 month
• Slight decreasing in hearing loss-3 months
• Dizziness- 3 months
• Facial fasciculation twitching- 3 months
• No facial numbness

3. Tinnitus Handicap Inventory

4. Dizziness Handicap Inventory

5. Speech audiometry

6. Pure tone audiometry

7. Pure tone audiometry

8. Gardner-Robertson grade

9. House-Brackmann scale

10. • Widened Right acoustic
porous
• Ice-cream cone
appearance
• No bony involvement
• Touching brainstem
• Minimal enhancement
CT scan

11. • Intracanalicular and extra
canalicular component
• Touching brainstem
• No cystic component
• Minimal enhancing
FSPGR CONTRAST

12. • Intracanalicular and extra
canalicular component
• Touching brainstem
• No cystic component
• Ice-cream cone appearance
• Impending 5th nerve
FIESTA sequence
LT. Fifth
nerve
RT. Fifth
nerve

13. Imaging -June 2020

14. Imaging conclusion
• RT. CP angle tumor
• Dm-16mm x 21mm x 13mm
• Dm of intracanalicular component 11mm x 9mm
• Indenting RT. middle cerebellar peduncle
• Indenting cisternal part of Vth nerve
• VIIth and VIIIth nerve separately not visualized
• No compression on 4th ventricle
• No internal cystic component
• Hypo on T1 as well as onT2
• Minimal enhancement
• Widened internal meatus
Imaging conclusion

15. Koos grading

16. Koos grading

17. Tumor grading

18. A. Observation
B. Surgery
C. Stereotactic Radiosurgery
Line of treatment

19. Surgical consultation
• Better go with radiation for hearing
preservation
• 7th and 8th nerve not separated out on imaging

20. Why we have chosen radiation
• Very small tumor
• Not visualized 7th and 8th nerve
• Solid variant
• < 2.5 cm
• Good hearing and facial function

21. Flickinger Algorithm

22. IRSA Algorithm

23. Tumor board decision
• After group discussion with neurosurgeon,
radiation oncologist and patient, board
decided to plan for stereotactic radiotherapy
• Patient was explained about complications
and outcome of each procedure
– Hearing preservation
– Facial numbness

24. Patient discussion
• Discussed about RT comparing with surgery
• Discussed about the procedure
• Discussed about hearing preservation
• Discussed about imaging and follow up
• Discussed about tumor response
• Discussed about need of surgery in future
• Discussed about post radiotherapy pain

25. TUMOR CONTROL
HEARING PRESERVSTION
TRIGEMINAL/FACIAL NERVE PAIN
Patient discussion

26. ISRS PRACTICE GUIDELINE
Dose selection

27. University hospital of wales protocol
Dose selection

28. Dose selection

29. • Planned for FSRT
• Plan multiple fraction
• 25Gy/5# - marginal dose
Radiation tumor board

30. Immmobilization and set up

31. • 1mm slice
• Contrast
• Vertex to neck
• With fraxion
Planning CT

32. MRI protocol
• T1/T2/FLAIR sequence- Usual sequence
• 3D FSPGR sequence- Normal anatomy
• FIESTA sequence- Cochlea and brain stem
• GRE sequence- Cystic changes/Hemorrhage
• 512x 512 matrix
• 1mm slice
• No gap
• No tilt
• Neutral neck
• FOV should include body contour nose, eye and skull

33. • CT AND MRI FUSION
Image fusion

34. • CTV delineation
• VOLUME- 1.682cc
• Multiplanar evaluation
Target delinetaion

35. • 1mm
• VOLUME- 2.776CC
PTV

36. Multiplanar CTV and PTV

37. Smooth your contour

38. The innervation of 8th nerve

39. Cochlea contouring
Contour
this only

40. OAR DELINEATIONOAR delineation
Cochlea
Brain
stem

41. • VMAT
• DCARC
• 3DCRT
• IMRT
Planning

42. Beam arrangement

43. SL NO PARAMETER VALUE
1 D MAX 29.83Gy
2 D95% 25.25Gy
3 D100% 24.18Gy
4 V95% 100%
5 V25 Gy[V100%] 97.5%
6 V110% 18.26%
7 V120% 0
8 V130% 0
1. Prescription Isodose level is usually not 100% PD covering 100% PTV
2. Often 95% PD covering 95% PTV or higher
3. Or 100% PD covering 95% PTV or higher.
Michael Torrens,/J Neurosurg (Suppl 2)/2014
PTV coverage index

44. • FORMULA
• VOLUME OF PRESCRIPTION ISODOSE/PTV VOLUME
• 3.214/2.776=1.15
• DESIRABLE=1
[Sonja Petkovska
Proceedings of the Second
Conference on Medical Physics
and Biomedical Engineering]
RTOG conformity index

45. • FORMULA
(VOLUME OF PRESCRIPTION ISODOSE IN AREA OF INTEREST)2
PTV VOLUME X VOLUME OF PRESCRIPTION ISODOSE
• 3.03x3.03/2.776X3.214=1.02
• IDEAL= > 0.85. AND <1
Michael Torrens,/J Neurosurg (Suppl 2)/2014
Paddick conformity index

46. • FORMULA
• MAXIMUM DOSE/PRESCRIPTION DOSE
• 29.83Gy/25Gy=1.19
• DESIRABLE = 1.1-1.3
HOMOGENITY index

47. • Dose fall off observation is very much needed in this
evaluation under headings
• Gradient index
• Difference between various isodose lines
• e.g between 80% and 60%- ideal- <2mm
• Between 80% and 40%- ideal- < 8mm
• For that reason we have to calculate equivalent
radius
Dose fall off

48. • To evaluate dose gradient we have to find out
difference between radius of various isodose line
• But none is iso spherical
• We have to find out equivalent radius from formula
• First find out the specified isodose volume
• Then calculate the radius
• V=4/3 πr3
• r= (3V/4π)1/3
Equivalent radius

49. SL NO PARAMETER VOLUME RADIUS
1 100% ISODOSE 3.214CC 0.91mm
2 80% ISODOSE 9.692CC 1.32mm
3 60% ISODOSE 18.835 CC 1.65mm
4 50% ISODOSE 25.834CC 1.83mm
5 40% ISODOSE 36.827CC 2.06mm
r= (3V/4π)1/3
Equivalent radius

50. • FORMULA
– Difference of equivalent radius of prescription
isodose and equivalent radius of 50% isodose
• 1.83mm=0.91mm
• 0.92mm
• It should be between 0.3 to 0.9
Gradient index

51. • BETWEEN 80% AND 60%- IDEAL-<2mm
– HERE- 0.33mm
• BETWEEN 80% AND 40%- IDEAL- <8mm
– HERE- 0.74mm
EORTC-22952-26001
Distance between various isodose lines

52. CONSTRAINTS

53. SL NO ORGAN DESIRABLE ACHIEVED
1 RT. EYE MAX <22.5Gy 1Gy
2 LT. EYE MAX <22.5Gy 1Gy
3 RT. OPTIC NERVE MAX <22.5Gy 1.2Gy
4 LT. OPTIC NERVE MAX <22.5Gy <1Gy
5 OPTIC CHIASM MAX <22.5Gy <2.8Gy
8 BRAIN STEM MAX 23-31Gy 27.19Gy
9 RT. COCHLEA MEAN <25Gy 20.35Gy
10 LT. COCHLEA MEAN <25Gy 1.31Gy
GG HANNA/CLINICAL ONCOLOGY/2016
OAR coverage

54. • MECHANICAL ISOCENTER CHECK
– WINSTON LUTZ TEST
• POINT DOSE VERIFICATION
• TOLERANCE-1MM
Travis R. Denton/JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS/2015
QA part

55. Dry run

56. • CBCT CORRECTIONS
Set-up verification

57. • HEXAPOD CORRECTIONS
Set-up verification

58. PREMEDICATION
• TAB. DEXAMETHASONE 8MG THRICE DAILY
STARTING DAY BEFORE
• TAB. ONDANSETRON 8MG THRICE DAILY
STARTING DAY BEFORE
• TAB. PAN 4O ONCE DAILY STARTING DAY
BEFORE
• DIABETES CARE IF
Pre medication-optional

59. • TAPER THE STEROID OVER A WEEK
• ANTI EMETICS
• PPI
Post medication-optional

60. • Imaging after 6 months
Adviced

61. Waiting for icecream to melt

62. Radiotherapy outcome grading

63. DOCTORS
• DR P S BHATTACHARYA
• DR C R KUNDU
• DR V K REDDY
• DR P MADHURI
• DR SAJAL KAKKAR
PHYSICISTS
• MR A C PRABU
• MR A SRINU
• MR Prasad
• DR ANIL KUMAR
TECHNOLOGIST TEAM
Acknowledgments