Stereotactic body radiotherapy for prostate cancer

Abstract

The term stereotactic implies that the target is localized relative to a fixed three-dimensional spatial coordinate system. Stereotactic body radiation therapy (SBRT) is defined as giving a high dose of radiation per fraction, in up to five fractions, using sophisticated image guidance to deliver a potent ablative dose to cancerous tissues while minimizing the risk to normal structures. The alpha-beta ratios for the rectum and bladder, both of which are late-responding tissues, are 2.5-5 Gy and 3-7 Gy, respectively. This unique biologic nature of prostate cancer explains the therapeutic gain with hypofractionation. These radiobiologic assumptions were supported by prospective randomized trials that used 2.5- 3.1 Gy per fraction.