10 may sbrt

Stereotactic body radiation
therapy (SBRT)
Dr Sadia Sadiq
PGR 2,INMOL

Historical Perspective
We should recognize and acknowledge
that Stereotactic Body Radiation
Therapy (SBRT) is an extension or
evolution of Stereotactic Radiosurgery
(SRS)

Why ?
If we acknowledge this evolution, we
should also provide EXTRA-ORDINARY
CARE for SBRT as demanded in
Stereotactic Radiosurgery (SRS)

Questions: Why is EXTRA-
ORDINARY
CARE necessary?
Why is EXTRA-ORDINARY
CARE needed ?

Stereotactic body radiation
therapy (SBRT)
Management and delivery of image
-guided high-dose radiation therapy with
tumor-ablative intent within a course of
treatment that does not exceed 5
fractions American Society of Therapeutic Radiology and Oncology (ASTRO)
Also called SART

Tumors include lung, liver, spine,
pancreas, kidney, and prostate.
Prospective trials have demonstrated
efficacy and acceptable acute and
subacute toxicities
Late toxicity requires further careful
assessment

Radiation: Fractionation
Standard fractionation:
 1.8-2.0 Gy a day, 5 days a week for 25-30
treatments
Conventional hypofractionation:
 3-5 Gy a day, 5 days a week for 10-15
treatments
Stereotactic radiotherapy:
 15-25 Gy a day, 1-3 days a week for 1-5
treatments

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

Methods Of Cell Kill in SBRT
DNA damage
Anti Angiogenesis
Endothelial cell Apoptoses

 1. Qualified personnel:
 a. Board-certified radiation oncologist b. Qualified medical physicist
 c. Licensed radiation therapist d. Other support staff as indicated
(dosimetrists, oncology
 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.

SBRT PHYSICS AND
TECHNOLOGY
 1. CT simulation: Assess tumor motion
 2. Immobilization: Minimize motion, breathing effects
 3. Planning: Small field dosimetry considerations
 4. Repositioning: High precision patient set-up:
Fiducial systems, IR/LED Active and Passive markers, US, Video
 5. Relocalization: Identify tumor location in the treatment field:
* MV/ KV Xray, Implanted markers and/or set-up fiducials
* Motion tracking and gating systems
* Real-time tumor tracking systems with implanted markers
 6. Treatment delivery techniques
 Adapted conventional systems
 Specialized SRT: Novalis, Cyberknife, Trilogy

4D CT Simulator
A technique that allow an
evaluation of the
motion of the target
Figure: Christopher Willey, MD, PhD

4D CT Simulator
The trace of the target motion
allow the creation of a
internal target volume
(ITV) for treatment
planning

Stereo Imaging
Technology:
To localized the target on
images On-Board Imager on
Linac In-Room Localizer

Breathing-related motion control devices
and systems fall into three general
categories:
(a) dampening,
(b) gating, and
(c) tracking or “chasing.”

Respiratory dampening techniques
 Include systems of abdominal compression intended to diminish
one of the largest contributors to breathing-related motion,
namely diaphragmatic excertion.

ABC:
 Also included in this category are the systems employing breath-
holding maneuvers to stabilize the tumor in a reproducible stage
of the respiratory cycle (e.g., deep inspiration).

Gating systems for SBRT
 It follow the respiratory cycle using a surrogate
indicator for respiratory motion, for example, chest
wall motion, and employ an electronic beam activation
trigger allowing irradiation to occur only during a
specified range of expected tumor locations.

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

SBRT:LUNG
Indications:
Stage I NSCLC
Pulmonary metastases

 One important observation from the Indiana
University studies was that although the
treatment was generally well tolerated,
 tumor location near large airways in the vicinity
of the pulmonary hilum (called the zone of the
proximal bronchial tree) was associated with a
markedly higher risk of toxicity.

RTOG 0236:
•59 patients
• Median age 72
• All pts inoperable
•T1 – 80%; T2- 20%
•Dose: 60Gy in 3 fxs (BED 180)
Median FU 3 yrs:
•Local control = 97.6%
•Distant mets = 22.1%
•Overall survival @3yrs = 55.8%
•Median survival = 48 months

SBRT: LIVER
 Underlying severe liver disease often renders
patients medically inoperable
 Other nonsurgical therapies have generally
achieved at best rather modest success in that
setting.

Challenges in Targeting Liver
Tumors
Limited visualization of the target
Liver deformation with respiration
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

Abdominal Compression
Abdominal belt with inflatable bladder
Inflation: 15-40 mmHg

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

SBRT:SPINE
SBRT is an emerging technology used for the
treatment of spinal tumors.
 Effective dose escalation
 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.

Indications for Spinal SBRT
Pain control in vertebral metastases
Malignant Epidural Spinal Cord
compression
Benign Spinal Cord Tumors

Dose volume constraints
 In a Randomized trail of 260 patients investigators
have not observed a single case of Myelopathy at 1
year with dose of 8Gy *1fr.
 Partial volume tolerance of the human spinal cord
to Radiosurgery was analyzed in 177 patients with
230 metastatic lesions.
The authors concluded that an acceptable estimate of
partial cord tolerance is 10 Gy to the 10% volume.
1.Rades D, Stalpers LJ, Veninga T et al. J Clin Oncol 23:3366–3375
2.Ryu S, Jin JY, Jin R et al 2007Cancer 109:628–636

 The a/b ratio of Prostrate Cancer is lower than for
most other tumors. Values between 1.2 and 3 Gy
are suggested.
 It is lower than surrounding normal tissues like
rectum (a/b of 4 Gy for late rectal sequelae).
 It is hypothesized that hypofractionation if
accurately delivered increases the tumor control by
sparing surrounding late responding normal tissues.
SBRT:PROSTRATE

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

SBRT: PANCREAS
Stereotactic body radiation therapy (SBRT) In
Pancreas is indicated for
1.Boderline resectable tumors to improve
resectability in Neo Adjuvuvant setting.
2.In Unresectable due to their lower life expectancy
to reduce 5 -6 weeks treatment to less than 5 days
3.In resectecd Ca Pancreas with positive margins.

Challenges of SBRT in Pancreas
 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.

SIDE EFFECTS
Radiobiology:
 Tumor vs. Normal Tissue
Normal Tissue Toxicity
 Lung: pneumonitis and fibrosis
 Pancreas: duodenum and stomach
 Spine lesions: cord
 Prostate: rectum and bladder
 Liver: normal liver (radiation induced liver
disease-RILD)

Stereotactic Body Radiation Therapy:
The Report of AAPM Task Group 101

The SBRT:Ultimate “Targeted
Therapy”

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