ESTRO 2025 - Abstract Book

S4414

Late-breaking abstracts

ESTRO 2025

4981

Proffered Paper Ultra-hypofractionated radiotherapy for localised prostate cancer: 10-year outcomes of the HYPO-RT-PC phase 3 trial (ISRCTN45905321) Per Nilsson 1 , Adalsteinn Gunnlaugsson 1 , Lars Beckman 2 , Anders Widmark 3 , Per Fransson 4 , Morten Hoyer 5 , Magnus Lagerlund 6 , Jon Kindblom 7 , Bengt Johansson 8 , Kirsten Björnlinger 9 , Claes Ginman 10 , Martha Olsson 11 , Måns Agrup 12 , Elisabeth Kjellén 1 , Björn Zackrisson 3 , Harald Anderson 13 , Björn Tavelin 14 , Lars Franzén 3 , Camilla Thellenberg Karlsson 3 1 Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Clinical Sciences, Lund University, Lund, Sweden. 2 Department of Oncology, Sundsvall Hospital, Sundsvall, Sweden. 3 Department of Diagnostics and Intervention, Oncology, Umeå University, Umeå, Sweden. 4 Department of Nursing, Umeå University, Umeå, Sweden. 5 Danish Centre for Particle Therapy, Aarhus University Hospital, Aarhus, Denmark. 6 Department of Oncology, Kalmar Hospital, Kalmar, Sweden. 7 Department of Oncology, Institute of Clinical Sciences, University of Gothenburg Sahlgrenska Academy, Goteborg, Sweden. 8 Department of Oncology, Örebro University Hospital, Örebro, Sweden. 9 Department of Oncology, Ryhov Hospital, Jönköping, Sweden. 10 Department of Oncology, Central Hospital, Karlstad, Sweden. 11 Department of Oncology, Central Hospital, Växjö, Sweden. 12 Department of Oncology, Linköping University Hospital, Linköping, Sweden. 13 Department of Cancer Epidemiology, Lund University, Lund, Sweden. 14 Cancercentrum, Umeå University Hospital, Umeå, Sweden Purpose/Objective The HYPO-RT-PC trial compares efficacy and safety between ultra-hypofractionated (UHF) and conventionally fractionated (CF) radiotherapy in men with intermediate-to-high-risk localised prostate cancer [1]. Here we report 10-year efficacy and toxicity outcomes. Material/Methods HYPO-RT-PC is a randomised, multicentre, open-label, non-inferiority phase 3 trial including 1180 men in the per-protocol population with localised prostate cancer. Patients were randomised to UHF (42.7 Gy in 7 fractions over 2.5 weeks) or CF radiotherapy (78.0 Gy in 39 fractions over 8 weeks). Androgen deprivation therapy (ADT) was prohibited. Primary endpoint was failure-free survival (FFS), defined as time to biochemical failure, clinical progression, ADT initiation, or prostate cancer-specific death. Secondary endpoints included biochemical failure, clinical progression, overall survival (OS), prostate cancer-specific survival, time to ADT, and toxicity. Kaplan Meier and Cox regression analyses were used to assess outcomes. Results At a median follow-up of 10.6 years, 178 primary events occurred in the UHF group versus 205 in the CF group. The 10-year FFS rates were 72% (95% CI 68–76) for UHF and 65% (61–69) for CF (log-rank p=0.12). The adjusted HR for FFS was 0.84 (95% CI 0.69-1.03), confirming non-inferiority. The Kaplan-Meier curves were similar up to approximately six years, after which they diverged, favouring UHF over CF (Fig. 1). The difference at 10 years was statistically significant (p=0.025). OS was similar between the two groups (log-rank p=0.34, HR=0.91; 95% CI 0.75– 1.11). At 10 years, OS was 81% (95% CI 78–84) in the UHF group and 79% (76–82) in the CF group. The cumulative incidence of prostate cancer-specific death at 10 years was identical at 4%. Freedom from ADT at 10 years was 77% in the UHF group and 75% in the CF group (log-rank p=0.36). There were no statistically significant differences in late GU and GI toxicity between the groups (Fig. 2). The cumulative 10-year incidence of late grade ≥2 GU toxicity was 27% in the UHF group and 28% in the CF group (log-rank p=0.78), while late grade ≥2 GI toxicity was 14% in the UHF group and 15% in the CF group (log-rank p=0.49).