Toxicity and patient-reported outcomes after moderately hypofractionated radiotherapy (60 Gy in 20 fractions) for prostate cancer: prospective observational study.

We investigated toxicity and patient-reported outcomes in patients with localized prostate cancer treated with moderately hypofractionated radiotherapy, focusing on clinically meaningful deterioration assessed using the minimum clinically important difference (MCID) at 24 months. Between January 2019 and December 2021, 58 patients were prospectively enrolled at a single institution and received volumetric-modulated arc therapy and image-guided radiotherapy, delivering 60 Gy in 20 fractions. The median follow-up period was 48 months. Toxicities were evaluated using the Common Terminology Criteria for Adverse Events version 5.0. Health-related quality of life (HR-QOL) was assessed at baseline and at 3, 6, 12, 24 and 36 months using the Short Form-8 Health Survey (SF-8) and the Expanded Prostate Cancer Index Composite (EPIC). Grade 2 acute gastrointestinal (GI) and genitourinary (GU) toxicities occurred in 0% and 5.2% of patients, respectively. Late Grade 2 GI and GU toxicities occurred in 1.7% and 6.9% of patients, respectively. No Grade ≥ 3 toxicities were reported. At 24 months, a ≥ 2 × MCID decline in SF-8 physical and mental component scores was observed in 12.2% (95% confidence interval [CI]: 3.2-21.2%) and 14.3% (95% CI: 4.5-24.1%), respectively. In the EPIC domains, ≥ 2 × MCID declines occurred in 23.8% (95% CI: 10.9-36.7%) for bowel and 8.5% (95% CI: 0.5-16.5%) for urinary summary scores. A 60 Gy regimen delivered in 20 fractions is feasible and well tolerated, with low toxicity and stable HR-QOL, although these preliminary findings are based on a limited observation period and sample size. Longer follow-up and larger studies are warranted.