Stereotactic body radiation therapy (SBRT) is a highly conformal form of radiation treatment that delivers a very high dose of radiation to an extracranial tumor target in only a few fractions. SBRT aims to ablate the tumor target using multiple, precisely aimed radiation beams that converge on the tumor. It provides an alternative to surgery for localized tumors, offering improved local tumor control compared to conventional radiation through dose escalation while sparing surrounding healthy tissues from damage. SBRT requires specialized equipment and planning to accurately deliver high radiation doses with minimal margins. Reported outcomes show it effectively controls tumors in the lung and liver with acceptable toxicity risks.

1. Stereotactic Body Radiation
Therapy (SBRT)
RadiantCare Radiation Oncology
James F Raymond MD

2. SBRT: What is it?
• Highly conformal radiation treatment confined to
an extracranial target
• Use of multiple radiation beams that converge
upon the target isocenter
• Very high dose radiation given in only a few
fractions with 2X-3X the biological effect
• Intended to ablate all cells within the target
volume

3. Rationale for SBRT
• Local control is poor after standard radiation
treatment for many extra-cranial tumors
• Local control can be improved with dose
escalation but there is risk of normal tissue injury
due inaccuracies in treatment delivery
• Improvements in the delivery of radiation therapy
now permit dose escalation while sparing injury
to surrounding normal tissues

4. Conventional Dose Distribution

5. SBRT Dose Distribution

6. Origin from Intracranial Treatment
• Stereotactic radiosurgery was first developed in
1951 by Swedish neurosurgeon
• Single treatment with doses intended to kill all
cells within an irradiated volume
• Utilization of an external 3D reference system
(stereotactic system) for accurate localization of
the target and for directing the radiation therapy

7. Stereotactic Methods
• Intracranial targets require fixation of the
stereotactic frame to the skull bone
• Extracranial applications preclude fixation and
the target can move
• Stereotactic body frames help to minimize the
internal motion of the target
• CT treatment planning and LINAC “on board” CT
imaging help to avoid missing the target

8. Brain vs Body Setup
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 2.

9. Geometric Verification
• SBRT coordinate system is based on the target
and not on normal anatomy
• The stereotactic reference system correlates the
LINAC and the CT scan images to locate the
target
• Imaging of the target during treatment delivery
permits a direct comparison to the reference
image which improves accuracy

10. Coordinate Systems
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 3.

11. Verification of Alignment
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 3.

12. Heterogeneous Dose Distribution
• Radiation resistance of many tumors is likely
due to hypoxic core
• SBRT increases the dose to the central parts of
the tumor by approximately 50% compared to
the periphery of the target
• This is accomplished by using multiple beams
converging at the center of the target

13. SBRT increases the dose within the target
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 4.

14. SBRT utilizes multiple beams
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 112.

15. Fractionation
• Single fraction schemes were initially employed
based on the experience of intracranial
radiosurgery
• A few fractions of very high dose per fraction
(hypofractionation) preferred due to toxicity
using single fraction schemes
• Few fractions better than many due to emphasis
on geometric accuracy and patient comfort

16. Equipment
• LINAC with multileaf collimator
• 3D or IMRT treatment capability
• CT for treatment planning
• Image Guided Radiation Therapy
– Fiducial markers or CBCT
• Internal Organ Motion Control
• Stereotactic Body Frame

17. Modern LINAC

18. LINAC with CBCT

19. Stereotactic Body Frame
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 5.

20. Tumor Types treated at the Karolinska
Hospital with SBRT from 1991-2003
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 6.

21. Summary
• SBRT is a good non-surgical option for
eradicating small volume tumors mostly in
the lung and liver
• Appropriate patient selection is important
• CT treatment planning is required
• Treatment delivery is complicated and
requires state-of-the-art treatment facilities

22. Case Examples
SBRT for Lung Cancer

23. Results of SBRT for
Early Stage Lung Cancer
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 104.

24. Results of SBRT for
Metastatic Lung Tumors
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 104.

25. Complications of Lung SBRT
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 105.

26. Case Example Lung SBRT
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 111.

27. Case Examples
SBRT for Liver Metastases

28. Single-institution Reports of
SBRT for Liver Metastases
Kavanaugh and Timmerman, Stereotactic Body Radiation Therapy 2005; pg 118.

29. Case Example of SBRT for Liver Metastases

30. Follow-up scans after SBRT