ESTRO 2025 - Abstract Book

S2060

Clinical - Urology

ESTRO 2025

3575

Digital Poster Ureter tolerance in patients treated with SBRT on abdominopelvic lymph nodes: analysis on dose-related late toxicity Chiara Mattioli 1 , Lucy A. van Werkhoven 2 , Maaike T.W. Milder 2 , Joost J. Nuyttens 2 1 Radiation Oncology, Azienda Ospedaliero Universitaria Careggi, Università di Firenze, Firenze, Italy. 2 Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center, Rotterdam, Netherlands Purpose/Objective: The goal of this study was to evaluate late ureteral toxicity in patients treated with stereotactic body radiation therapy (SBRT) for abdominopelvic lymph node (A-P LN) oligometastases and to correlate this with the dose received by the ureter. Material/Methods: We retrospectively reviewed treatment plans of patients who received SBRT between 2011 and 2023 on A-P LN oligometastases from colorectal and prostate cancer and from patients who were included in the STEAL study (NL58442.078.17). Patients whose planning CT showed that one or both ureters received a dose ≥ 10 Gy were included. Ureters within the 10 Gy isodose were delineated, and dosimetric data was obtained. Late toxicity (>3 months from SBRT) was recorded and graded (G) according to the Common Terminology Criteria for Adverse Events v5.0. Doses were recalculated to an EQD2 with a/b =3 Gy (Gy 3 ). We compared our results with the ureter constraints of two studies: a D max of 45 Gy in 5 fractions (108 Gy 3 ) and D 0.1cc of 40 Gy in 5 fractions (88 Gy 3 ) 1,2 Results: We included 122 patients and 137 ureters, with the majority having prostate (70%) and colorectal (25%) cancer and a median follow-up of 28 months. Treatment was delivered with the following schedules: 45 Gy in 5 fractions (84%), 35 Gy in 7 fractions (12%), and 48 Gy in 6 fractions (4%). The median D max and D 0.1cc of the ureter were 60 Gy 3 (IQR 27-105) and 42 Gy 3 (IQR 21-85), respectively. A total of 32 patients received a D max exceeding 108 Gy 3 and 30 patients a D 0.1cc exceeding 88 Gy 3 . Three patients (2%) had G3 ureteral obstruction with hydroureteronephrosis, requiring JJ catheter placement. The ureters of these 3 patients received a D max of 121, 97 and 74 Gy 3 , respectively. The D 01cc in these 3 ureters was 112, 76 and 48 Gy 3 , respectively. These 3 patients had a previous history of surgery and/or chemotherapy. Late grade ≤2 toxicities were: urinary incontinence (N=2), hematuria (N=1), urinary tract obstruction (N=1), urinary retention (N=1), nocturia (N=1) and bladder cramps (N=1) (Table 1). No grade ≥4 toxicities were observed.