S1197
Clinical - Urology
ESTRO 2026
Phurailatpam 3 , Ritesh Mhatre 3 , Balakrishnan Arun 4 , Pallavi Singh 1 , Sakshi Dubey 1 , Abhilash Gavarraju 1 , Tejshri Telkhade 1 , Ketaki Adsul 1 , Gagan Prakash 5 , Mahendra Pal 5 , Amandeep Arora 5 , Ankit Misra 5 , Santosh Menon 6 , Aparna Katdare 7 , Archi Agrawal 8 , Shyam C Sundar 9 , Srinivas Chilukuri 10 , Indranil Mallick 2 1 Radiation Oncology, Tata Memorial Centre, Mumbai, India. 2 Radiation Oncology, Tata Medical Center, Kolkata, India. 3 Medical Physics, Tata Memorial Centre, Mumbai, India. 4 Medical Physics, Tata Medical Center, Kolkata, India. 5 Surgical Oncology, Tata Memorial Centre, Mumbai, India. 6 Pathology, Tata Memorial Centre, Mumbai, India. 7 Radiology, Tata Medical Center, Mumbai, India. 8 Nuclear Medicine, Tata Memorial Centre, Mumbai, India. 9 Medical Physics, Apollo Proton Cancer Centre, Chennai, India. 10 Radiation Oncology, Apollo Proton Cancer Centre, Chennai, India Purpose/Objective: Randomised data is lacking for SBRT in high-risk and node-positive prostate cancer treated with pelvic RT. We report acute and 1-year adverse effects (AE) from the phase III multicentric randomised PRIME trial (NCT03561961). Material/Methods: Men with NCCN high-risk or N+ prostate cancer planned for curative RT were randomised 1:1 across 3 centres to moderate (MHRT) or extreme (SBRT) hypofractionated RT. Prostate was prescribed 68Gy/25# or 62Gy/20# MHRT daily or 36.25Gy/5# SBRT on alternate days or weekly, with 50Gy/25# or 44Gy/20# MHRT or 25Gy/5# SBRT to the pelvis and at least 24 months of ADT for all patients. AEs were graded using CTCAE v5.0 at RT completion, at 6 weeks, and then 3 to 6 monthly. We report the acute (within 3 months of RT) and one-year (3 to 12 months) urinary and gastrointestinal AE from the trial, while follow up continues for survival outcomes. Results: From June 2018 to August 2024, 526 patients were randomised to MHRT (n=264) or SBRT (n=262). Total 509 received RT and were eligible for safety analysis. About 55% patients had cT3b-T4 disease, and 24% had a prior TURP (Figure 1). Planned SBRT was completed in the test arm without interruptions for any patient. Acute grade 3 AEs were low, with GI 0.6% (n=3, MHRT=2 SBRT=1) and urinary 0.2% (n=1, MHRT). Grade 2+ acute AEs were similar with MHRT and SBRT for GI (14.7% vs 14.9%, p=0.99) and urinary (28.2% vs 23.8%, p=0.27) symptoms. Weekly SBRT was associated with significantly lower gr2+ acute GI effects than alternate day schedule (3.0% vs 19.1%, p=0.004). Most AEs recovered within the first 3 months of RT (Figure 2), with 1-year grade 3 AEs only 0.6% (n=2 urinary, SBRT; 1 GI, MHRT). Cumulative 1-year grade 2+ AEs were similar for MHRT and SBRT for GI (4.6% vs 6.5%,
p=0.43) and urinary (10.9% vs 14.3%, p=0.28) effects. Gr2+ 1-year urinary AEs were higher in patients with prior TURP (21.8% vs 9.1%, p=0.02) Gr2+ 1 year urinary and GI AEs were higher in those with Acute gr2+ GI and urinary AEs (p<0.001 each), whereas SBRT scheduling (weekly or alternate day) showed no difference in 1-year AEs.
Conclusion: Safety analysis from the multicentre PRIME trial showed excellent tolerance of SBRT in locally advanced prostate cancer, with <1% severe adverse effects. Acute and 1-year gastrointestinal and urinary effects were similar for MHRT and SBRT schedules of
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