According to findings from the PACE-B clinical trial, no increase in toxicities was observed with ultrahypofractionated radiotherapy versus conventionally fractionated or moderately hypofractionated radiotherapy for prostate cancer (Lancet Oncol. 2019;20[11]:1531-1543).

“Ultra-hypofractionated stereotactic body radiotherapy would allow shorter treatment courses but could increase acute toxicity compared with conventionally fractionated or moderately hypofractionated radiotherapy,” explained Douglas H. Brand, MRes, The Royal Marsden Hospital, London, United Kingdom, and colleagues asthe purpose of the trial. 

Between August 7, 2012 and January 4, 2018, a total of 874 patients with low- or intermediate-risk prostate adenocarcinoma were recruited from 37 centers to participate in the international, phase 3 PACE-B study. The patients were randomly assigned to receive conventionally fractionated or moderately hypofractionated radiotherapy (n = 441) or stereotactic body radiotherapy (n=433). 

Ultimately, 432 (98%) of 441 patients received at least 1 fraction of conventionally fractionated or moderately hypofractionated radiotherapy, and 415 (96%) of 433 patients received at least 1 fraction of stereotactic body radiotherapy.

Freedom from biochemical or clinical failure was the primary end point. Additional end points were the worst grade ≥2 severe Radiation Therapy Oncology Group gastrointestinal or genitourinary toxic effects score up to 12 weeks after radiotherapy.

Results showed that 10% of patients in the stereotactic body radiotherapy arm experienced grade ≥2 gastrointestinal toxic events versus 12% in the conventionally fractionated or moderately hypofractionated radiotherapy arm. Grade ≥2 genitourinary toxic events occurred in 23% and 27% of patients, respectively. There were no treatment-related deaths.

“Previous evidence…suggested higher patient-reported toxicity with ultrahypofractionation. By contrast, our results suggest that substantially shortening treatment courses with stereotactic body radiotherapy does not increase either gastrointestinal or genitourinary acute toxicity,” concluded Mr Brand and his co-investigators.—Kaitlyn Manasterski