Top Line: What are the differences in acute toxicity following moderately hypofractionated IMRT or SBRT for prostate cancer?
The Study: You probably know the PACE-B trial pretty well by now. It compared IMRT and SBRT for low to intermediate risk prostate cancer not requiring ADT. PACE-C was a similarly designed trial that enrolled 1192 patients with unfavorable intermediate risk (62.4%) or high risk (36.2%) prostate cancer. Of note, only 5.7% had Gleason 4+4 or higher disease, and MRI-defined extracapsular extension was present in 28%. They were randomized to moderately hypofractionated IMRT (60 Gy in 20 fractions) or SBRT (40/36.25 Gy in 5 fractions). Patients in both arms received at least 6 months of ADT. The majority of patients in both arms were treated on a conventional LINAC (96% IMRT, 84% SBRT), but 6% and 10% in the SBRT arm were treated on MR LINAC or CyberKnife, respectively. More SBRT patients had a planning MRI (70% v 41%). Rectal spacers were not used. This report described acute toxicity outcomes. During the 12 weeks after treatment, there was no difference in the cumulative rates of RTOG grade 2+ GU toxicity (28% SBRT v 27% IMRT). At the 12 week mark, residual grade 2+ GU toxicity was 7% with SBRT and 4% with IMRT. Cumulative CTCAE grade 2+ GU toxicity was reported by 34% after SBRT and 28% after IMRT. At week 12, residual grade 2+ GU toxicity was 10% with SBRT and 7% with IMRT. There was no difference in cumulative RTOG grade 2+ GI toxicity (13% SBRT v 11% IMRT), but CTCAE grade 2+ GI toxicity was higher after SBRT (17% v 10%). However, at the 12 week mark 2% in each arm reported residual grade 2+ CTCAE GI toxicity.
TBL: Initial toxicity outcomes from PACE-C show comparable acute GU and GI outcomes following moderately hypofractionated IMRT and SBRT for intermediate to high risk prostate cancer. | Tree, Lancet Oncol 2025
The Study: You probably know the PACE-B trial pretty well by now. It compared IMRT and SBRT for low to intermediate risk prostate cancer not requiring ADT. PACE-C was a similarly designed trial that enrolled 1192 patients with unfavorable intermediate risk (62.4%) or high risk (36.2%) prostate cancer. Of note, only 5.7% had Gleason 4+4 or higher disease, and MRI-defined extracapsular extension was present in 28%. They were randomized to moderately hypofractionated IMRT (60 Gy in 20 fractions) or SBRT (40/36.25 Gy in 5 fractions). Patients in both arms received at least 6 months of ADT. The majority of patients in both arms were treated on a conventional LINAC (96% IMRT, 84% SBRT), but 6% and 10% in the SBRT arm were treated on MR LINAC or CyberKnife, respectively. More SBRT patients had a planning MRI (70% v 41%). Rectal spacers were not used. This report described acute toxicity outcomes. During the 12 weeks after treatment, there was no difference in the cumulative rates of RTOG grade 2+ GU toxicity (28% SBRT v 27% IMRT). At the 12 week mark, residual grade 2+ GU toxicity was 7% with SBRT and 4% with IMRT. Cumulative CTCAE grade 2+ GU toxicity was reported by 34% after SBRT and 28% after IMRT. At week 12, residual grade 2+ GU toxicity was 10% with SBRT and 7% with IMRT. There was no difference in cumulative RTOG grade 2+ GI toxicity (13% SBRT v 11% IMRT), but CTCAE grade 2+ GI toxicity was higher after SBRT (17% v 10%). However, at the 12 week mark 2% in each arm reported residual grade 2+ CTCAE GI toxicity.
TBL: Initial toxicity outcomes from PACE-C show comparable acute GU and GI outcomes following moderately hypofractionated IMRT and SBRT for intermediate to high risk prostate cancer. | Tree, Lancet Oncol 2025