Stereotactic Body Radiation Therapy (SBRT) or Alternative Fractionation Schedules

The use of hypofractionated regimens for the treatment of tumors with radiation has come full circle. After the discovery of X-rays and their utilization for cancer treatment, the initial fractionation schemes were primarily hypofractionated in nature. However, due to technical limitations and associated toxicities, more protracted fractionated regimens eventually became the foundation for modern radiation therapy. With the advance of imaging and radiation delivery systems, interest in more hypofractionated approaches was revived. Stereotactic ablative radiation therapy (SABR; also referred as stereotactic body radiation therapy, SBRT) is the most abbreviated form of hypofractionation, typically utilizing 1–5 fractions for treatment. Its strengths include high rates of tumor control via a convenient, noninvasive outpatient procedure. Toxicities related to high, ablative radiation doses still are a potential concern; however, recent clinical trials for a variety of tumor sites have shown good outcomes in properly selected patients. This chapter will discuss the potential for SBRT/SABR to improve the therapeutic response. The use of SBRT/SABR regimens to treat lesions within the lung, liver, spine, and prostate will be reviewed. Due to more mature data in regard to the safety and efficacy, cost-effectiveness of the treatment, and potential for immunomodulatory effects, SBRT/ SABR has become more wildly utilized in cancer treatment.