Twice- vs. thrice-weekly moderate hypofractionated radiotherapy for prostate cancer: does overall treatment time matter?

To evaluate the influence of overall treatment time (OTT) in disease control, acute, and long-term side effects with moderate hypofractionated external beam radiotherapy (RT) for prostate cancer (PCa) delivered either twice- or thrice-a-week.

157 patients with localized PCa were treated consecutively with 56 Gy in 4 Gy/fraction delivered either twice (86 patients, from 2003 to 2010, group-1) or thrice a week (71 patients, from 2010 to 2017, group-2) using IMRT or VMAT techniques. Gastrointestinal (GI) and genitourinary (GU) toxicities were scored according to the CTCAE v3.0 grading scale. Median follow-up was 110 and 56 months for groups 1 and 2, respectively.

At 6 weeks, patients treated thrice-a-week experienced higher acute ≥ grade-2 GU toxicity compared to those treated twice a week (25.4% vs 5.8%, p = 0.001) even though none presented ≥ grade-3 GU or GI toxicity in the thrice-a-week group. The 5-year ≥ grade-2 late GU toxicity-free survival was higher in group-1 (95.9 ± 2.3%) than in group-2 (81.5 ± 4.9%, p = 0.003), while no differences in ≥ grade-2 late GI toxicity-free survival were observed between both groups (97.5 ± 1.7% vs. 97 ± 2.1% for groups 1 and 2, respectively). The 5-year biochemical relapse-free survival (bRFS) was not different for patients treated twice compared to those treated thrice-a-week (80.6 ± 4.5% vs. 85.3 ± 4.8%, respectively, p = 0.441), as much as for patients treated in > 5 weeks vs. those treated in ≤ 5 weeks (81.3 ± 4.4% vs. 84.4 ± 5.1%, respectively, p = 0.584).

In this retrospective hypothesis-generating analysis, less vs. more than 5 weeks OTT may increase acute and late GU toxicities without significantly improving bRFS in patients treated to high effective doses (> 80 Gy) with moderate hypofractionated RT. Prospective trials evaluating the impact of OTT on hypofractionated schedules for PCa are warranted.

Journal of cancer research and clinical oncology. 2019 Mar 18 [Epub ahead of print]

Vérane Achard, Sandra Jorcano, Michel Rouzaud, Lluís Escudé, Raymond Miralbell, Thomas Zilli

Radiation Oncology Division, Geneva University Hospital, 1211, Geneva 14, Switzerland., Radiation Oncology, Teknon Oncologic Institute, Barcelona, Spain., Radiation Oncology Division, Geneva University Hospital, 1211, Geneva 14, Switzerland. .