S1234
Clinical - Urology
ESTRO 2026
Oct 1 [cited 2025 Nov 11];120(2):S1.2. Murthy V, Mallick I, Gavarraju A, et al. Study protocol of a randomised controlled trial of prostate radiotherapy in high-risk and node-positive disease comparing moderate and extreme hypofractionation (PRIME TRIAL). BMJ Open. 2020;10(2):e034623. Published 2020 Feb 28. Keywords: High-risk prostate, Proton therapy, Prospective 10-Year Survival and Toxicity Outcomes of SBRT for Low and Favorable Intermediate-Risk Prostate Cancer in a Large Cohort CLAUDIA COLOM PLA 1 , MARÍA CERROLAZA PASCUAL 1 , ANA GALÁN GARCÍA 1 , CLAUDIA LABORDA DÍAZ 1 , ANDREA OCHOA CONRADO 1 , VICTORIA NAVARRO AZNAR 2 , CRISTINA GARCÍA AGUILERA 1 , ARANTXA AYETE ANDREU 1 , JAVIER TOMÁS ANCHUELO LATORRE 1 , AGUSTINA MÉNDEZ VILLAMÓN 1 , REYES IBÁÑEZ CARRERAS 1 Digital Poster 2607 1 RADIATION ONCOLGY, MIGUEL SERVET UNIVERSITARY HOSPITAL, ZARAGOZA, Spain. 2 RADIATION ONCOLGY, LOZANO BLESA UNIVERSITARY HOSPITAL, ZARAGOZA, Spain Purpose/Objective: Stereotactic body radiation therapy (SBRT) has gradually been recognized as an effective treatment for localized prostate cancer. The low α / β ratio of prostate tissue supports the adoption of ultrahypofractionated radiotherapy schedules, which not only provide biological advantages, but also offer benefits in terms of shorter treatment time, patient convenience, and optimized resource use. Material/Methods: Between 2015 and 2023, 439 patients with localized prostate adenocarcinoma (low- or favourable intermediate-risk) were treated in this single- institution and single-arm study. The treatment volume included the prostate ± 1 cm proximal of seminal vesicles, without prophylactic pelvic irradiation. A total dose of 35 Gy in 7 alternate-day fractions was prescribed. SBRT was delivered using a standard CT-guided linear accelerator. The primary endpoint was progression-free survival (PFS), assessed at 10 years. Acute genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Statistical analyses used χ² , t tests, and Kaplan–Meier estimates, with p < 0.05 considered statistically significant. Results: The median age was 73 years, and the median baseline PSA was 7.19 ng/mL. Among the cohort, 184
acute or late events were rare (<1%) in the MHRT cohort, whereas none were reported with IMPT over 12 months. On multivariable analysis, IMPT significantly reduced acute GU AEs (OR 0.22, 95% CI 0.08–0.62, p=0.004) and GI AEs (OR 0.04, 95% CI 0.01– 0.28, p<0.001). Acute grade ≥ 2 AEs predicted late grade ≥ 2 AEs (OR 4.6, 95 % CI 1.4–15.2, p = 0.01), suggesting that early toxicity was strongly associated with subsequent grade ≥ 2 events.Table1:
Figure 1:
Conclusion: This comparative analysis in high-risk disease demonstrates that CBCT-guided IMPT is associated with substantially fewer early urinary and gastrointestinal AEs compared to MHRT. This underscores the need for prospective evaluation of IMPT in high-risk and node-positive prostate cancer. References: 1. Efstathiou JA, Yeap BY, Michalski JM, Horick N, Zietman AL, Christodouleas JP, et al. Prostate Advanced Radiation Technologies Investigating Quality of Life (PARTIQoL): Phase III Randomized Clinical Trial of Proton Therapy vs. IMRT for Localized Prostate Cancer. Int J Radiat Oncol Biol Phys [Internet]. 2024
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