Fifteen to the fossa.

Top Line: Can hypofractionation be used for post-prostatectomy radiation?

The Study: We’ve seen several hypofractionation trials for post-prostatectomy radiation of late, the common theme being acute toxicity is favorable while rates of late grade 3+ toxicity may be higher than expected. Here’s a single-arm, single-center, phase 2 trial of hypofractionated post-prostatectomy radiation. All patients had a bone scan and pelvic MRI staging prior to enrollment. They used the RTOG prostate fossa CTV with a 5 mm PTV, and elective nodal coverage was not included. The prescription was 51 Gy in 15 fractions, which is an EQD2 (alpha/beta=2) of 68.8 Gy. The primary endpoint of acute grade 2+ GU toxicity was estimated to be ~15%. In total, 61 patients were enrolled, and most (93%) received salvage (as opposed to adjuvant) radiation. The rate of acute grade 2+ GU toxicity was 11.5% with only 1 grade 3 GU event. Late grade 3+ events were low with only one grade 3 GU event and no grade 3 GI events--rates notably lower than the ~10% rate seen in several other trials. In multivariable analysis, rectum V20 and V26 were predictors of acute GI toxicity, but there were no significant dosimetric predictors of acute GU toxicity.

TBL: Acute toxicity from hypofractionated post-prostatectomy radiation appears favorable, but more data from randomized trials is needed to assess late toxicity and efficacy outcomes. | Teixeira Leite, Int J Radiat Oncol Biol Phys 2020