S1290
Clinical - Urology
ESTRO 2026
Conclusion: In this robustness-inclusive multicentre comparison within the setting of a randomised clinical trial, proton- based WPRT substantially reduced low- and intermediate-dose exposure to bowel and bladder while maintaining target coverage comparable to photon therapy. These advantages persisted under realistic geometric and anatomical uncertainties, supporting the continued inclusion of patients in the trial. Keywords: Prostate cancer, Proton therapy, Clinical trial Hypofractionated Radiotherapy VS Conventional Fractionation in Organ-Preserving Treatment for Muscle-Invasive Bladder Cancer (MIBC) Xiaoye Su 1 , wenjue zhang 1 , lingling feng 1 , xiaoyong xiang 1 , yutong tan 1 , lining chen 1 , junqin lei 1 , tongda lei 1 , nan hu 1 , huanrong jiang 2 , yi liu 2 , haitao li 2 , dongwen wang 2 , qin xiao 1 , jun tian 2 , jing jin 1 1 Radiotherapy center, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China. 2 Department of Urology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China Digital Poster 4201 Purpose/Objective: For patients with muscle-invasive bladder cancer (MIBC) who are ineligible for or decline radical cystectomy (RC), trimodality therapy (TMT) centered on radiotherapy offers a bladder-preserving alternative with potential outcomes comparable to RC. With ongoing evolution in radiotherapy regimens—from conventional to hypofractionated schedules and from regional to selective nodal irradiation—we evaluated real-world outcomes of hypofractionated versus conventional radiotherapy within a TMT framework. Material/Methods: We conducted a retrospective analysis of MIBC patients (cT1–4N0–+M0–1) treated between July 2019 and July 2024 in the Department of Radiation Oncology at the Cancer Hospital of the Chinese Academy of Medical Sciences, Shenzhen. All patients had declined or were deemed unsuitable for RC following multidisciplinary discussion and received radiotherapy as part of TMT. Radiotherapy was delivered as either 66 Gy in 33 fractions (conventional fractionation) or 55 Gy in 20 fractions (hypofractionation), both with elective pelvic nodal irradiation. Survival outcomes were compared using
the log-rank test. Results: Among the 32 included patients, the median follow-up was 28.5 months (range, 3–43.7 months), and the median age was 72 years (range, 51–87). Most patients were male (75.0%) and had urothelial carcinoma (87.5%); four had neuroendocrine histology. Five patients (15.6%) had metastatic disease at presentation. Prior systemic therapy was administered in 84.4% of patients, including immunotherapy in 43.7%. Nine patients (28.1%) had recurrent disease before radiotherapy.Hypofractionated radiotherapy (55 Gy/20 fx) was used in 20 patients (62.5%) and conventional fractionation (66 Gy/33 fx) in 12 (37.5%). Overall, 13 patients (40.6%) received pelvic nodal irradiation, and 21 (65.6%) received concurrent chemotherapy or immunotherapy.The median overall survival (OS) for the entire cohort was 16.7 months, with a 2-year OS rate of 81.1%. The hypofractionated group showed significantly superior 2-year progression-free survival (PFS) compared to the conventional group (76.2% vs. 36.4%, P = 0.017), with no significant difference in OS. No Grade 3 or higher genitourinary or gastrointestinal toxicities were observed. All patients retained their bladder through the follow-up period.
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