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Role of SBRT in lung cancer
1. ROLE OF SBRT IN
LUNG CANCER
By
Dr. Ayush Garg
Senior Resident
2. Learning Objectives for JRs
What is SBRT?
Why need of SBRT?
Difference between Conventional RT and SBRT
Steps of SBRT
Indications of SBRT
Advantages & Disadvantages of SBRT
Learning Objectives for SRs
Various dose regimes
OAR dose tolerances
Evidences of SBRT
3. Introduction
• SBRT is a noninvasive treatment
involving the precise delivery of
ablative dose radiation
• Compared with fractionated radiation,
SBRT achieves superior local control
and survival
• SBRT (also known as SABR) uses short courses of very high (ablative),
highly conformal, and dose-intensive RT precisely delivered to limited-size
targets.
• Current standard-of-care for early-stage, nonoperative NSCLC is
stereotactic body radiation therapy (SBRT)
4. Types of lesions
Peripheral lesions
• They are located > 2 cm from the primary bronchi or trachea
Central lesions
• Located within 2 cm of the proximal bronchial tree and/or
abutting mediastinal pleura
Ultra-Central lesions
• Lesions abutting the proximal bronchial tree
5. The black dashed line defines the location of tumors that are central relative to the proximal bronchial tree.
The term central has been widened to include the region within 2 cm in all directions of any mediastinal critical
structure, including the bronchial tree/trachea, esophagus, heart, brachial plexus, major vessels, spinal cord,
phrenic nerve, and recurrent laryngeal nerve. The region shaded red shows the trachea and main bronchi, and
lesions with a PTV which overlaps this region are considered as ultracentral.
b Example of an ultracentral tumor (planning target volume in red, and main bronchi/trachea in yellow).
c Example of a central tumor
8. The work flow
Pre-SBRT
work up
Simulation
(+/- 4DCT)
Tumor &
OAR
contouring
Plan
analysis &
acceptance
Trial setup &
off line
CBCT
Treatment
delivery &
review
Follow up &
data
collection
9. Pre requisites for SBRT
• Equipment
• Staff teaching and training
• Patient selection for SBRT
• Patient counselling
• Treatment planning
• Dose and fractionation
• Radiotherapy planning steps
• Inter- and intra-fraction image guidance
• Quality assurance
• Follow-up
10. Equipment
Mandatory
• C-arm linear accelerator with volumetric in-room image guidance
• Respiration correlated 4D-CT
Recommended
• Dedicated C-arm stereotactic linear accelerator (more advanced
IGRT, more precise accuracy)
• High-resolution MLC <10 mm
11. Staff teaching and training
• Written departmental protocols
• Multi-disciplinary project team for SBRT implementation and
application
• Structured follow-up for clinical outcome assessment
12. Patient selection for SBRT
SBRT is recommended in the NSCLC for patients with
Stage I and II (T1–3,N0,M0)
NSCLC who are medically inoperable
High risk- elderly
Refuse surgery after appropriate consultation
SBRT has no established role in small cell lung cancer
PFT (FEV1 or DLCO
< 40%)
DM/CAD
Cerebral disease
Pul. HTN
PS 0-2
Able to lie flat for at
least one hour
13.
14. Early-Stage NSCLC (Stage I, selected node-negative Stage IIA)
• SBRT is recommended for patients who are medically inoperable or who
refuse to have surgery after thoracic surgery evaluation.
• SABR is also an appropriate option for patients with high surgical risk (able to
tolerate sublobar resection but not lobectomy [eg, age ≥75 years], poor lung
function).
• SABR has achieved good primary tumor control rates and overall survival,
and higher than conventionally fractionated radiotherapy, although not
proven equivalent to lobectomy
NCCN Guidelines Version 7.2019 Non-Small Cell Lung Cancer
16. Patient Positioning and Immobilization
• Stable and reproducible patient positioning is essential. If
possible, patients should be positioned with both arms above
the head as this position permits a greater choice of beam
positions.
• Reproducible setup can be achieved using a stable arm
support, in combination with knee support to improve patient
comfort.
19. Fusion Images
CT scan
• Planning CT scans should be acquired in treatment position,
and incorporate techniques for evaluating motion compensation
• A planning CT scan should include the entire lung volume, and
typically extends from the level of the cricoid cartilage to the
second lumbar vertebra
• Slice thickness of 2–3 mm is recommended
• IV contrast should be used
• 4D-CT is recommended
20. Fusion Images
PET scanning
The equipment used for patient immobilisation during PET scans
should be identical to that used for CT scanning and treatment
21. Target Volume Definitions
GTV
• CT with the settings: W= 1600 and L = 600 for parenchyma, and W=
400 and L = 20 for mediastinum should be used
• Elective nodal irradiation is not indicated in any patient
CTV
• In SBRT treatments, CTV margins are generally not used
ITV
• Target representing the range of GTV motion through the breathing
cycle
PTV
• ITV + 3 to 10 mm margin; Respiratory motion is a patient-specific
factor which should be determined before treatment, typically using a
pre-treatment 4D-CT or 4D PET/CT scan
22. Target Volume Definitions
Passive motion compensation strategies
• Abdominal compression
• Internal target volume (ITV) concept
• Mid-ventilation concept
• Jet-ventilation
Active motion compensation strategies
• Gating
• Breath hold
• Tracking
Application of one (either active or passive) 4D motion compensation
strategy is highly recommended
23. • Deep inspiration breath hold (DIBH) reduces tumour motion
while increasing the lung volume, resulting in decreased doses
to lung, and often also to the heart
24. Target volumes definition
PRV
For serial organs, including the spinal cord, the main bronchi, the
brachial plexus, the oesophagus and large blood vessels, the use
of a PRV might be helpful, since it reduces the probability of over
dosage
25. A 57-year-old man with medically inoperable NSCLC of the right upper lobe,
treated on an SBRT protocol: 30 Gy/1 fx.
(a) From the CT simulation, this image depicts the GTV during free breathing (red),
at maximum inhalation (green), and maximum exhalation (blue).
(b) ITV (lime) was generated by combining GTVs. PTV (light blue) = ITV + 5 mm.
(c) Isodose distribution using a 6-arc plan, 6 MV photons, prescribed to the 80%
isodose line
26. Stephans et al. l SBRT for Central Lung Tumors l 10/ 4/11 l 16
Beam Placement
29. Commonly Used Doses for SABR
Total Dose # Fractions Example Indications
25–34 Gy 1 Peripheral, small (<2 cm) tumors, esp.
>1 cm from chest wall
45–60 Gy 3 Peripheral tumors and >1 cm from chest
wall
48–50 Gy 4 Central or peripheral tumors <4–5 cm,
especially <1 cm from chest wall
50–55 Gy 5 Central or peripheral tumors, especially <1
cm from chest wall
60–70 Gy 8–10 Central tumors
NCCN Guidelines Version 7.2019 Non-Small Cell Lung Cancer
PRINCIPLES OF RADIATION THERAPY
30. Treatment Planning
Mandatory
• 3D conformal treatment planning
• Type B algorithms
• Respiration correlated 4D-CT imaging
• ITV based motion management strategy
Recommended
• Dynamic IMRT planning (VMAT)
• Use of a fixed dose inhomogeneity in PTV
31. Treatment Planning
Dose calculations
Dose calculation algorithms currently used for lung radiotherapy
generally take into account changes in electron transport due to
density variations, and are referred to as so-called type B or
Monte Carlo based algorithms
32. Radiotherapy Planning
• Tumour and nodal changes
• Inter-fractional tumour shifts
• Intra-fractional tumour shifts
• Intra-fractional respiratory and cardiac motion
• Anatomical changes during fractionated radiotherapy
34. Tumour and nodal changes
Inter-fractional tumour shifts
• Inter-fractional shifts between primary tumour and vertebra
positions range from 5 to 7 mm on average (3D vector), but
may be as high as 3 cm
• Image guidance and patient setup corrections are essential
35. Tumour and nodal changes
Intra-fractional tumour shifts
• The intra-fractional target shifts are usually of small magnitude,
ranging from 0.15 to 0.21 cm
• Intra-fractional drifts increase when treatment times exceed 34
min
36. Tumour and nodal changes
Intra-fractional respiratory and cardiac motion
• Increased motion has been observed in lower-lobe tumours, for
smaller primary tumours and for infra-carinal lymph nodes
• For tumours close to heart or aorta, cardiac-induced motion can
exceed respiratory motion due to large inter-patient variability,
patient-specific motion assessment should be performed
38. Red Shell
• The Red Shell representing high-risk tissue is shown in red surrounding
the clinical target volume (CTV) shown in gray.
• The serial critical organs are shown in yellow on the right.
• The Red Shell is composed of two sub-shells, the Inner Red Shell (the
smaller red ring surrounding the CTV) and the Outer Red Shell (the bigger
red ring surrounding the Inner Red Shell).
• The internal boundary of the Inner Red
Shell is the CTV surface.
• The external boundary of the Inner Red
Shell is the planning target volume (PTV)
surface.
39. Red Shell
• The external boundary of the Outer Red Shell is where the biologically
effective dose (BED) drops to the constraint dose.
• The Red Shell is curved inward on the right side.
• This is the result of careful planning to spare a critical serial organ (yellow)
in near proximity.
• As a result, the dose may need to protrude outward on the opposite side,
generating a bigger Red Shell in that direction, at the ‘‘cost’’ of sparing the
critical organ.
42. Follow up
Mandatory
• Follow-up according to published guidelines
• FDG-PET imaging in case of suspected local recurrence
Recommended
• Routine biopsy confirmation of imaging-defined local failure only
in patients who are likely to undergo salvage therapy
43. Quality Assurance
Mandatory
• Intensified quality assurance (mechanical accuracy of 1.25 mm and a
dosimetric accuracy of 3% in a lung phantom inside the treatment field)
• Small field dosimetry detectors for commissioning
• Quality assurance of in-room image-guidance systems and of the 4D-
CT scanner
• Weekly checks of the mechanical accuracy of the delivery system
• Daily quality checks of the alignment of the IGRT system with the MV
treatment beam
45. A 7-year follow-up showed that overall survival rates were 55.7% at 5 years and
47.5% at 7 years.
In 12 patients (18.5%), a second primary lung carcinoma developed after SABR
at a median of 35 months (range, 5–67 months); 27% (18/65) had disease
recurrence a median of 14.5 months (range, 4.3–71.5 months) after SABR.
• In conventionally fractionated
RT,
• 3-year survival is only about
20% to 35%
• Local failure rates of about
40% to 60%
• In SBRT
• Generally more than 85%, and
about 60% at 3 years (median
survival, 4 years), respectively
In Medically inoperable patients
46. Indiana (Timmerman JCO 2006; Fakiris, IJROBP 2009)
• n=70
• T1–3N0 (≤7 cm)
• 60–66 Gy in 3 fx over 1–2 weeks.
• Three-year LC 88%, CSS 82%, OS 43%, regional failure 9%, and
distant failure 13%.
• Patients with central tumors had increased risk of grade 3–5 toxicity
(27% vs 10%).
• Established “no-fly-zone” of 2 cm surrounding proximal
bronchial tree for 3-fraction treatment.
47. Onishi (Cancer, 2004)
• n=245
• T1–2N0 treated
• 18–75 Gy in 1–22 fx
• LF was 8% for BED ≥100 Gy vs 26% for BED <100 Gy.
• Three-year OS was 88% for BED ≥100 Gy vs 69% for BED
<100 Gy.
48. RTOG 0236 (Timmerman 2010)
• T1–3N0 (≤5 cm), medically inoperable tumors >2 cm from
proximal bronchial tree treated
• SBRT 20 Gy × 3 over 1.5–2 weeks (54 Gy applying
heterogeneity correction).
• GTV = CTV. PTV = 0.5 cm axial margin and 1 cm
superior/inferior margin.
• 5-year LC 93%, LRC 62%, 31% DM, DFS 26%, OS 40%.
49. RTOG 0915 (Videtic IJROBP 2015)
• Phase II randomized study of 34 Gy in 1 fraction vs 48 Gy in 4
fractions
• Medically inoperable T1-3N0 (≤5 cm) NSCLC
• Single fraction arm had lower risk of serious adverse events
(10.3 vs 13.3%).
• 2-year primary control, OS, and DFS were 97% vs 93%, 61% vs
77%, and 56% vs 71%, respectively.
50. RTOG 0618 (Timmerman ASCO 2013)
• Medically operable T1-T3N0 (≤5 cm) NSCLC >2 cm from
proximal bronchial tree
• 60 Gy in 3 fractions (54 Gy with heterogeneity correction).
• 2-year primary failure rate 7.8%, local failure (including
ipsilateral lobe) 19.2%, OS 84%. 16% grade 3 toxicity
51. RTOG 0813 (Bezjak ASTRO 2016)
• Phase I/II dose escalation trial for medically inoperable early-
stage NSCLC with centrally located lesions (<2 cm from the
bronchial tree)
• Arm I- 57.5 Gy (n=38), Arm II-60 Gy (n=33).
• Dose escalated from 50 Gy in 5 fractions to 60 Gy in 5 fractions.
• 2 yr LC 88–89%, PFS 52–55%, OS 70–73%, grade 3 toxicity 6–
7%
53. SBRT VS SURGERY
Two randomized trials of surgery vs SBRT for operable early-
stage NSCLC failed to accrue (STARS and ROSEL)
54. Combined ROSEL/STARS analysis (Chang Lancet Oncol
2015):
• n=58 patients from two trials
• T1-T2 (<4 cm) N0 medically operable NSCLC
• SBRT (54 Gy in 3 fractions, 50 Gy in 4 fractions if central) vs
lobectomy and mediastinal lymph node dissection.
• 3-year OS improved for SBRT (95%) vs surgery (79%). Grade
3–4 toxicity 10% for SBRT vs 44% for surgery.
SBRT VS SURGERY
55. • JoLT-Ca STABLE-MATES trial (NCT02468024)
• VALOR (Veterans Affairs Lung cancer surgery Or stereotactic
Radiotherapy trial, NCT02984761)
• SABRTOOTH (NCT02629458)
Trials under going
SBRT VS SURGERY
56. Conclusion
It is a form of high precision radiotherapy delivery technique
• Needs to account for tumor motion
• Needs to be accurate
• Needs to have reproducible setup prior to treatment
Indications
• Stage I–II, inoperable, T1-3N0M0 Definitive SBRT not 3D
• Medically inoperable
• Operable disease who are high risk, elderly
• Refuse surgery
57. SABR for Node-Negative Early-Stage NSCLC
• BED ≥100 Gy are associated with significantly better local control and survival
• For central and ultra-central tumors 4 to 10 fraction regimens are effective and
safe
• SABR is most commonly used for tumors up to 5 cm in size
SBRT has a Developing role
• Boost following definitive chemoradiation in management of LA-NSCLC
• Re-irradiation of locally recurrent disease
• Intrathoracic oligometastases from various primary histologies
Editor's Notes
Window width is range and window level is center point of width
current physical and especially clinical data do not support the superiority of one particular strategy.
Multiple co planar and non co planar beams are used
