Stereotactic Body Radiation Therapy

Selected Readings

AAPM TG-101: Stereotactic Body Radiation Therapy (external link)

Overview

Stereotactic Body Radiation Therapy (SBRT), refers to the use of highly conformal low fraction (5 or less) therapy techniques when used outside of the cranium. The term SBRT is increasingly being replaced by the term SAbR (Stereotactic Ablative Radiotherapy) both because the procedure does ablatively destroy tumor tissue and because the pronunciation of the acronym (Pronounced: Sabre) is faster to say, and sounds cooler, than "S-B-R-T."

Treatment Sites

Breast

Background: Breast cancer is not commonly treated with SAbR/SBRT as a primary treatment but may be used as a boost. Very little data is available on this topic.

Common Prescriptions: 20-30Gy delivered in 3 to 5 fractions

Gynecological

Background: SAbR/SBRT is not typically used as a primary therapy for gynecological cancers but may be used for slavage/re-irradiation.

Common Prescriptions: 15Gy delivered in 3 fractions

Outcomes: Population size for salvage radiation studies are small but local control appears to be good (~80%). Normal tissue toxicity may be a concern.

Head and Neck

Background: Head and neck cancers are not commonly treated with SAbR/SBRT but data does exist on its use in salvage/re-irradiation.

Common Prescriptions: 18-40Gy delivered in 3-5 fractions

Outcomes: Local control for these salvage cases is generally strong (70-80%).

Liver

Background: Both primary and metastases may be treated with SAbR/SBRT in patients who are unfit for surgery (e.g. tumor near major vessels).

Common Prescriptions: Up to 60Gy delivered in 3 to 6 fractions

Lung

Background: Lung cancers, both early stage primary and metastasis, are among the most common locations for SAbR/SBRT. Lung SAbR/SBRT may be preferred over surgery for metastatic disease that is centrally located, includes lesions in both lungs, or have previously undergone lobectomy. Centrally located tumors, those within 2cm of the trachea, primary bronchus, or esophagus, require special care as the location induces significant risk of normal tissue toxicity.

Common Prescriptions:

Primary: 45-60Gy in 3-5 fractions

Metastasis: Many schedules are used, 50-55Gy delivered in 5 fractions is common

Outcomes:

Primary cancers experience good to excellent local control (up to 90%) at one year.

Metastasis experience good to excellent levels of local control (up to 90%) at three years.