S1132
Clinical - Urology
ESTRO 2026
Material/Methods: We conducted a retrospective analysis of two
institutional cohorts (Institut du Cancer de Montpellier, France [Center 1]; Rigshospitalet, Denmark [Center 2]) treated with the ETHOS™ system (Varian) between March 2021 and June 2023. When prophylactic pelvic lymph node irradiation (45–50 Gy) was indicated, the bladder boost (up to 63–64 Gy) was delivered sequentially in Center 1 and as a simultaneous integrated boost in Center 2. The primary objective was tolerance and dosimetric benefits of adaptation; secondary objectives included OS, PFS, and local PFS. Results: 49 patients (mean age: 74.4 year) were included (25 from Center 1, 24 from Center 2). 8 patients (16.3%) received a hypofractionated treatment (20 fractions) without pelvic irradiation; the remainder received 32 to 35 fractions. 30 patients (61.2%) underwent pelvic irradiation. Concomitant chemotherapy was administered to 22 patients (88.0%) in Center 1 versus 4 (16.7%) in Center 2 (see Table 1).
At 18 months, concomitant chemotherapy was associated with superior PFS (87.3% vs. 44.1%, p=0.01) and lPFS (96% vs. 48.3%, p=0.007). No other parameter was correlated with survival results. Conclusion: CT-guided oART provides consistent dosimetric advantages, favourable tolerance, and encouraging survival outcomes, particularly in patients receiving concomitant chemotherapy. References: 1. Liu H, Schaal D, Curry H, Clark R, Magliari A, Kupelian P, et al. Review of cone beam computed tomography based online adaptive radiotherapy: current trend and future direction. Radiat Oncol. 2 sept 2023;18(1):144. 2. Zlotta AR, Ballas LK, Niemierko A, Lajkosz K, Kuk C, Miranda G, et al. Radical cystectomy versus trimodality therapy for muscle- invasive bladder cancer: a multi-institutional propensity score matched and weighted analysis. Lancet Oncol. juin 2023;24(6):669 - 81. Keywords: Bladder cancers, online adaptive radiotherapy Poster Discussion 233 Three-fractions Linac-Based Prostate SBRT Using 4D Transperineal Ultrasound Monitoring: Preliminary Clinical Outcomes and Analysis of Motion Patterns Federica Ferrario 1 , Valeria Faccenda 2 , Nicola Vergari 3 , Chiara Chissotti 3 , Lorenzo De Sanctis 1,3 , Giulia Rossano 1,3 , Riccardo Ray Colciago 3 , Denis Panizza 2 , Stefano Arcangeli 1,3 1 Radiation Oncology Department, IRCCS San Gerardo dei Tintori, Monza, Italy. 2 Medical Physics Department, IRCCS San Gerardo dei Tintori, Monza, Italy. 3 School of Medicine and Surgery, Univerity of Milan Bicocca, Milan, Italy Purpose/Objective: This prospective study evaluates side effects (SE), quality of life (QoL), and intra-fraction motion in patients treated with prostate stereotactic body radiation therapy (SBRT) with curative intent.
The tumor was staged as cT1 for 5 patients (10.2%), cT2 for 40 patients (81.6%) and cT3 for 8 patients (8.2%). Only one patient was cN+. Mean treatment duration was 29 minutes. Treatment was delivered with an adapted plan in 100% of sessions in Center 1 and 86.6% in Center 2.The median follow-up was 17.7 months.There was no grade 4-5 toxicity but 49% of acute and 26% of late grade 2+ GU toxicities, and 17% of acute with no late grade 2+ GI toxicities.For bladder volume (mean PTV 318 cc), oART improved V95% coverage by 6.5% (92.5% vs. 99%, p<0.001). For pelvic lymph node volume (mean PTV 717 cc), V95% coverage improved by 3.6% (95% vs. 98.6%, p<0.001). Organs-at- risk sparing was significant, with reductions in rectum V50Gy (10% to 6.6%, p=0.004), intestine V30Gy (261 to 238 cc, p=0.008), and intestine V45Gy (139 to 121 cc, p=0.002) (see Figure 1).
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