Phase I study of stereotactic body radiotherapy following radical prostatectomy.

TPS158Background: Although multiple Phase I/II studies demonstrate safety and low rates of toxicity following stereotactic body radiotherapy (SBRT) to the intact prostate, there are limited data on hypofractionation and SBRT after prostatectomy. This Phase I study was performed to evaluate acute toxicity associated with dose escalation from 3.6 Gy per fraction to 7.1 Gy per fraction to the prostate bed in the post-prostatectomy treatment of prostate cancer. We hypothesize that the toxicity of escalating the dose per fraction to the prostate fossa in the post-operative setting will be well tolerated; and we expect toxicity to be comparable to normal fractionation schedules. Methods: This study (NCT02446366) was designed to look at acute toxicity, defined as toxicity that occurred within the first 10 weeks of RT, of different dose fractionation schemes in the post-prostatectomy setting. The doses chosen for dose escalation on this study are based on an equivalent biological effective dose to a previously pu...