Short course, long wait.
Top Line: Can hypofractionation be used for post-prostatectomy radiation?
The Study: Despite the success of moderate and extreme hypofractionation for intact prostate cancer, the prostate fossa has been stubbornly resistant to change. Yes, there have been several reports of hypofractionated post-prostatecomy radiation (including SBRT) with favorable acute toxicity. However, many of these also noted higher than expected late GI and GU toxicity. Currently, NRG GU-003 is comparing 66.6 Gy in 37 fractions to 62.5 Gy in 25 fractions. Here’s a trial that explored the shortest tolerated course when treating the prostate fossa alone (no nodes and no ADT). The target was the standard RTOG consensus CTV with a 5-7 mm margin, and it was prescribed 56.6 Gy in 20 fractions, 50.4 Gy in 15 fractions, or 42.6 Gy in 10 fractions. The latter regimen was used for an expansion cohort to evaluate acute toxicity and quality of life, and most patients (23/32, 72%) were treated in that arm. Acute toxicity was acceptable with just one (3%) acute dose-limiting event (grade 3 diarrhea) in the 15-fraction arm. As with other trials, though, late grade 3+ events (9.4%) were higher than expected.
TBL: Late toxicity outcomes from randomized trials of hypofractionated post-prostatectomy radiation are needed before incorporating this technique in routine practice. | Wages, Int J Radiat Oncol Biol Phys 2020