This document provides an overview of stereotactic body radiotherapy (SBRT). It begins with the history and introduction of SBRT, explaining how it differs from other radiotherapy modalities. It describes how SBRT works through its biological effects on tumor cells and blood vessels. Simulation, planning, patient immobilization and motion management are discussed. Common SBRT dose fractions and indications for various tumor sites are summarized, including lung, liver, spine, prostate and pancreas. Key challenges and dose constraints for each site are highlighted.

1. STEREOTACTIC
BODY
RADIOTHERAPY
Dr.Brijesh Maheshwari(jr-1)
Moderator- Dr. Piyush Sir, Dr.Ayush sir,
Dr.Rashika Ma’am

3. Topics that will be covered…..
HISTORY AND INTRODUCTION
WHAT IS SBRT AND HOW IT IS DIFFERENT FROM
OTHER MODALITIES
HOW IT WORKS(Radio-Biology)
HOW IT IS EXECUTED (Simulation and planning)
INDICATION
SITE WISE DISCUSSION

4. Historic Background
• The first one to combine stereotactic
methodology with radiation therapy was Swedish
neuro-surgeon LARS LEKSELL. He performed
first treatment in 1951.
• LEKSEL continued his work and built the first
isotope radiation machine in 1968,the gamma
knife.

5. SBRT is….
the term applied in the United States by the ASTRO
for the management and delivery of
1.image-guided
2.high-dose radiation therapy
3. with tumor-ablative intent
4. within a course of treatment
5.does not exceed 5 fractions.
6. Real time motion management
7.Computed assisted robotic delivery

6. Stereotactic refers to using a precise three
dimensional mapping technique to guide
procedure
SRS SRT SBRT
conformal
irradiation of
defined target
volume in a
single session
in cranium.
delivery of highly
conformal radiation
to defined target
volume in cranial
sites in multiple
fraction using non
invasive positioning
technique.
Is atreatment
modality that involves
the delivery of very
high individual doses
of radiation to tumors
in various extra cranial
sites with high
precision in multiple
fraction

10.  The biological mechanisms of these new modalities
have been unclear.
 DNA damages by direct effect of radiation alone
cannot account for the high efficacy of SBRT and
SRS
 Evidence now indicates that SBRT with doses higher
than about 10 Gy per fraction induces severe vascular
damages.
• The role of 4 Rs and the LQ model is limited in SBRT
and SRS.

11. • Lee et al. observed that delivery of an ablative dose of radiation
of 15–25 Gy in an animal model resulted in a considerable
increase in Tcell priming in draining lymphoid tissue, which in
turn led to reduction or eradication of the primary tumor or
distant metastasis in a CD8+ Tcell dependent fashion.
• GarciaBarros et al. demonstrated that exposure of mouse MCA129
fibrosarcoma and B16 melanoma cells to single doses of 15–20 Gy
was followed by a rapid wave of endothelial apoptosis at 1–6 h after
irradiation, which was followed by death of the tumor cells at 2–3
days after irradiation.

12. Rationale of SBRT
Conceptual theories of cancer growth and numerous
lines of evidence behind use of SBRT for metastatic
lesions are
 The Empiric Or Phenomenological,
 The Patterns-of-failure Concept,
 The Theory Of Oligo metastases,
 A Lethal Burden Variation Of The Norton-simon
Hypothesis, Or
 Immunological Enhancement.

13. A Lethal Burden Variation Of The Norton-
simon Hypothesis
• Tenets of this hypothesis has two goals
1)to reduce thetumor burden in such a way that
the remaining cancer cells within in the body
enters into a state of higher growth fraction thus
become more susceptible to cytotoxic
treatment.
2)to prevent or delay as long as possible the lethal
tumor burden that is fatal to patient

14. Methods Of Cell Kill in SBRT
• DNA damage
• Anti Angiogenesis
• Endothelial cellApoptosis

16. SBRT guidelines
1.Qualified personnel(qualified medical physicist,
licensed radiation therapist, board certified radiation
oncologist)
2. Ongoing machine quality assurance program;
3. Documentation in accordance with the ACR Practice
Guideline for Communication: Radiation Oncology;
4. Quality control of treatment accessories;
5. Quality control of planning and treatment images;
6. Quality control of treatment planning system;
7. Simulation and treatment systems based on actual measurement of
organ motion and setup uncertainty.

17. SBRT(physics and technology)
1. Immobilization
2.CT simulation
3. Planning
4. Repositioning
5. Re-localization
6. Treatment delivery techniques by
Specialized SBRT models: Novalis, Cyberknife

18. SIMULATION
1. Positioning and immobilization

19. 2. Respiratory tracking (gating) and simulation
a) Dampening
b)Gating
c)tracking or “chasing.”

20. • Ablative intent
• Dose inhomogeneity inside the PTV is
acceptable
• Maximum point dose up to 160% of Prescription
Dose within PTV is common.
• Minimize the volume of normal tissue irradiation
outside of the PTV(from entrance and exit of
beams, scatter radiation
3.TreatmentPlanning

21. The trace of the target motion allow the
creation of a internal target
volume (ITV) for treatment
planning

22. 4D CT based planning

23. 4.Treatment Verification
• Precision should be validated with each treatment
session by QC process both during and subsequent
fractions
• KBCT images should be taken on daily basis.

24. Patient Selection
• In several reports, the eligibility criteria in
oligometastatic tumors were
1)limited number of metastases (one to five)
2)limited tumor diameter (<4 cm)
3)a locally controlled primary tumor
4)no other metastatic sites
5) controlled primary
6)favorable histology
7) young age
8) good performance status (PS) of the patient

25. INDICATIONS
• The most common indications for SBRT are
the treatment of
a)non-metastatic primary cancer
b)oligo-metastases (that is, metastases that
are limited in number and/or organ sites).

26. Clinical Experience with Stereotactic Body
Radiation Therapy in Selected Sites
1)Lung
2)Liver
3)Spine
4)Prostate
5)Pancreas

27. SBRT LUNG

28. INDICATIONS
1 . Stage INSCLC
2 . Pulmonarymetastases

29. STEPS
1.Simulation
2.floroscopy to see the tumor motion in all
directions.
3.if tumor movement is more than
8mm then dampening with
abdominal compression.
4. Acquisition of slow CT in free breathing
time.

30. Abdominal Compression
• Abdominal belt with inflatable bladder
• Inflation: 15-40 mmHg

31. DOSE PRESCRIPTIONS
• Prescription should be such that BED >
100Gy
1. 12Gy in 4 fractions
2. 20 Gy in 3 fractions
3. 10Gy in 2 fractions

32. • The local recurrence rates were 8.4% in patients who
received a biological effective dose (BED) of 100 Gy
or more at the isocenter, and 42.9% in patients
receiving less than 100 Gy in BED.
• The local control rate was 95% median follow-up of
17.5 months and severe toxicity occurring at a median
of 10.5 months in 17% of those patients with peripheral
lesions versus 46% with central lesion.
1.Onishi H, Shirato H, Nagata Y,Hiraoka M, Fujino M, Gomi K et al (2007 )J
Thorac Oncol 2(7 Suppl 3):S94
•2.Timmerman R, McGarry R, Yiannoutsos C, et al..J Clin Oncol 2006;24(30):4833–4839

34. PULMONARY METS
• There are several reports on SBRT for metastatic lung cancer
.
• Up to two lesions were simultaneously treated in most of
these reports, except for that by Okunieff (up to five lesions).
The local control rate was more than 60% andthe overall survival
rate was more than 30% at 2 years.
• These outcomes were thought to becomparable to surgical
metastatectomy.

35. •SBRT: LIVER

36. Challenges in Targeting Liver Tumors
• Limited visualization of the target
• Changes in GI organ luminal filling
Critical structures (stomach) may change in shape
and position between planning and treatment
• Interfraction target displacement with respect to
bony anatomy

37. First Liver SBRT Experience
• 50 patients treated to 75 lesions with SBRT
for primary and metastatic liver tumors
• 15 to 45 Gy, 1-5 fractions
• Mean follow-up of 12 months
• 30% of tumors demonstrated growth arrest, 40%
were reduced in size, and 32% disappeared by
imaging studies
• 4 local failures (5.3%)
• Mean survival time was 13.4 months
• Blomgren, et. al., J
Radiosurgery, 1998

40. SBRT:SPINE

41. SBRT is an emerging technology used
for the treatment of spinal tumors.
• For patients who are not candidates for
conventional radiotherapy
• To improve the quality of life for patients who
may be spared a prolonged treatment
course.
• Acute Radiation toxicity is reduced.

42. INDICATIONS
• Pain control in vertebral metastases
• Malignant Epidural Spinal Cord compression
• Benign Spinal Cord Tumors

43. VERTEBRAL METS
 Pain control was higher than 90% with single doses over 16
Gy at 1 year(1).
 Strong trend toward increased pain control with higher
radiation dose .
 Higher Radiosurgery dose requirements (>20 Gy) for local
control with higher incidences of vertebral compression
fracture in up to 40% of the patients(2)
1. Gerszten PC et al (2005) Single-fraction Radiosurgery for the treatment of spinalbreast metastases. Cancer
104(10):2244–2254
2.Yamada Y et al (2008) High-dose, single-fraction image-guided intensity-modulated radiotherapy for metastatic spinal
lesions.
• Int J Radiat Oncol Biol Phys 71(2):484–490

44. • Most critical challenge is to minimize the risk
of spinal cord injury.
• Possible exacerbating factors
 Previous Neurotoxic chemotherapy
 Post surgery (Sub clinical vascular injury)
 Prior spinal trauma

45. DOSE CONSTRAINTS
• The Partial volume spinal cord tolerance dose
is 10 Gy to the 10% spinal cord volume.
• It is defined from 6mm superior to the
target volume to 6 mm inferior to the target
volume
• 10 Gy to the volume of 0.35 cc of the
spinal cord

46. SBRT PROSTATE

47. Indications
Primary treatment for organ confined low risk
prostrate cancer
Dose escalation for intermediate and high risk
prostrate cancer

48. Steps
1.Gold Fiducial placement under trans rectal
USG guidance ( 2 at base and 1 at apex. Each
fiducial 1.1mm thickness and 3mm length)
2.Simulation with full bladder
3.Planning CT scan with IR marker guidance

49. Dose Prescription
Dose of 35- 38Gy in 5 daily fractions as primary
treatment for low risk Prostrate cancer.(1)
Dose of 50Gy in 5 fractions as dose escalation (2)
1.Katz A, Santoro M, Ashley R, et al.. BMC Urol 2010;10:1.
2.Boike TP, Lotan Y, Chinsoo Cho L, et al. J Clin Oncol
2011;29:2020– 2026.

50. Dose volume constraints
1.Rectum were such that the V50% <50%,
V80% <20%, V90% <10%,and V100% <5%.
2.The bladder DVH goals were V50% <40% and
V100% <10%.
3.The femoral head DVH goal was V40% <5%.

52. SBRT:PANCREAS

53. Indications
 Boderline Resectable Pancreatic Ca
 Unresectable Pancreatic Ca

54. Challenges
 The head of the pancreas, where majority of tumors
reside, is in close proximity to the C-loop of the
duodenum
 Delivery of conventionally fractionated radiation
(1.8–2 Gy/day) to more than 50 Gy results in
damage to the small bowel such as ulcerations,
stenosis, bleeding, and perforation.
 The pancreas move with respiration, as well as
with peristalsis that is not easily predictable.

55. UCLA Technique
1.Logistically, 2–3 gold fiducials are placed directly
into the tumor under CT guidance for targeting
purposes.
2.A custom immobilization device is created for
each patient
3. Four-dimensional CT (4D-CT) images are used
for treatment planning. FDG-PET images are also
used for treatment planning

56. 4.An internal target volume (ITV) is
contoured based on the 4D-CT.
5. The ITV is expanded by 0 –3 mm (except for
expansion into the duodenum or stomach) to
form the PTV

57.  Dose of 36 Gy in three fractions is prescribed to the
isodose surface which covers the 95% of the PTV.
 No more than 50% of the contoured duodenum risk
object receives more than 21 Gy. For pancreatic head
lesions
 The dose to the contralateral duodenal wall closest to the
GTV is limited to a total dose of 18 Gy

59. Complications
• SBRT for lung tumors can potentially result in clinically
significant lung toxic effects, such as collapse of
airways, atelectasis, fibrosis and symptomatic
pneumonitis.
• SBRT for spinal tumors can result in minor acute or sub
acute nonneurologic complications such as esophagitis,
mucositis, dysphagia, diarrhea, lethargy, wound break
down, nausea, vomiting, noncardiac chest pain, mild
skin hyperpigmentation, trismus, transient laryngitis,
and idiopathic vasculitis.

60. • SBRT for pancreatic cancer is associated with
considerable toxic effects, which are related to the
proximity of the pancreas to various serial-
functioning structures such as the stomach and
small bowel.
• For patients with HCC, the reported rates of toxic
effects are relatively low.