S1233
Clinical - Urology
ESTRO 2026
Mini-Oral 2585 IMPT vs. IMRT in High-Risk Prostate Cancer: Early Safety outcomes from Propensity-Matched Comparison of Two Prospective Studies: The PROTO-PRIME Study Srinivas Chilukuri 1 , Sham sundar C 1 , Priyamvada Maitre 2 , Moses Arunsingh 3 , Vasanthapriya Subramani 2 , Abhilasha Sinha 1 , Manikandan Arjunan 4 , Reena Phurailatpam 5 , Divya Patil 2 , Vineeth Kumaar 1 , Dayananda Phurailatpam 4 , Indranil Mallick 1 , Vedang Murthy 2 1 Radiation Oncology, Apollo Proton Cancer Centre, Chennai, India. 2 Radiation Oncology, Tata Memorial Centre, Mumbai, India. 3 Radiation Oncology, Tata Medical Centre, Kolkata, India. 4 Medical Physics, Apollo Proton Cancer Centre, Chennai, India. 5 Medical Physics, Tata Memorial Centre, Mumbai, India Purpose/Objective: Proton therapy did not demonstrate reduction in adverse events (AEs) over IMRT in low and intermediate-risk prostate cancer1, and remains untested in high-risk or, node-positive cancers requiring pelvic irradiation (WPRT). This study compared early safety outcomes of CBCT-guided, moderately hypofractionated intensity-modulated proton therapy (IMPT) treated on a prospective PRO- Cube registry (CTRI/2022/01/039842) study with propensity-matched patients treated with moderately hypofractionated IMRT (MHRT) enrolled in the multicentric randomized PRIME trial2 (NCT03561961). Material/Methods: Consecutive patients with high-risk or node-positive prostate adenocarcinoma receiving IMPT for prostate ± WPRT were analysed for AEs (CTCAE v5.0) and matched 1:2 with PRIME trial MHRT patients using logistic-regression derived scores (caliper<0.2) with WPRT, TURP, and age as covariates. Planning goals and dose guidance for targets and organs of interest were stringently applied and adhered to in both cohorts. The primary endpoints were cumulative grade ≥ 2 genitourinary (GU) and gastrointestinal (GI) AEs at 3 months and 1 year, and the secondary endpoint was point-prevalent grade ≥ 2 AEs at 12 months. Results: A total of 204 patients were included, with 68 treated using IMPT and 136 with MHRT (Table 1), achieving excellent balance across all matching variables.Acute grade ≥ 2GU and GI AEs were significantly lower with IMPT compared with MHRT (GU 14.7% vs 28.9%, p=0.036; GI 0% vs 17.0%, p<0.001). The 1-year cumulative and point-prevalent grade ≥ 2 GU and GI AEs remained low and comparable between groups (13.2% and 2.9% with IMPT vs 17.0% and 5.2% with MHRT; and 4.4% and 0% with IMPT vs 9.6% and 2.9% with MHRT, respectively) as shown in Figure 1. Grade 3
endpoints include biochemical relapse-free survival (bRFS), pelvic progression-free survival, time to systemic therapy, time to castration resistance, cancer-specific survival, overall survival, safety, and quality of life. Toxicity is graded with CTCAE v5.0, and survival estimated using Kaplan–Meier methods. The planned sample size is 534 patients across 17 centres. Results: A total of 168 patients have been enrolled. High-risk disease represented 72.6% (n=122), while 27.4% (n=46) had intermediate-risk BCR. Nodal status was pN0 in 57.2% and pNx in 42.8%. Median age was 68 years (IQR 63–73), median PSA at inclusion 0.34 ng/mL (range 0.26–0.49), and median interval from surgery to BCR 18.5 months. PET/CT was performed in 66.7% (n=112), almost all with PSMA tracers. Hypofractionated SRT was used in 69.6% (n=117), and elective pelvic irradiation in 33.3% (n=56). At data cut- off, 92.7% (76/82) of patients in the 6-month arm and 81.4% (70/86) in the 24-month arm had completed or were receiving protocol treatment. After a median follow-up of 14 months (IQR 9–16), one biochemical relapse, no local or pelvic recurrences, one metastatic event, and one non–cancer-related death were documented. Grade ≥ 3 toxicity was uncommon (0.6%, n=1), and no treatment-related deaths occurred. Conclusion: URONCOR 06-24 is the first phase III randomized trial stratifying patients by risk group to compare short- versus long-term ADT combined with SRT for BCR after prostatectomy. Recruitment and treatment implementation demonstrate feasibility across centres, with an excellent early safety profile and minimal high-grade toxicity. Ongoing accrual and extended follow-up will clarify whether prolonged ADT provides superior 5-year MFS and additional clinically meaningful benefits. References: 1. González-San Segundo C, López Campos F, Gómez Iturriaga A, et al. A randomised trial of short- vs long- term androgen deprivation with salvage radiotherapy
for biochemical failure following radical prostatectomy: URONCOR 06-24. BJU Int. 2024;134(4):568-577.
doi:10.1111/bju.164842. González San Segundo C, López-Campos F, Gómez Iturriaga A, et al. Duration of androgen deprivation therapy with salvage radiotherapy in patients with prostate cancer and biochemical recurrence after surgery: Initial recruitment data in the phase III URONCOR 06-24 trial. Actas Urol Esp (Engl Ed). 2025;49(7):501823. doi:10.1016/j.acuroe.2025.501823 Keywords: ADT, Prostate bed, Salvage radiotherapy
Made with FlippingBook - Share PDF online