S1211
Clinical - Urology
ESTRO 2026
Digital Poster Highlight 2061 Clinical outcomes of dose-escalated radiotherapy for muscle-invasive bladder cancer Li Chan 1 , Anzela Anzela 1 , Viet Do 1 , Karen Wong 1 , Felicia Roncolato 2 , Joseph Descallar 3 , Matthew Stanowski 4 , Paul Sved 5 , Mark Sidhom 1 1 Radiation Oncology, Liverpool and Macarthur Cancer Therapy Centres, Sydney, Australia. 2 Medical Oncology, Liverpool and Macarthur Cancer Therapy Centres, Sydney, Australia. 3 Biostatistics, Ingham Institute, Sydney, Australia. 4 Urology, Liverpool Hospital, Sydney, Australia. 5 Urology, Royal Prince Alfred Hospital, Sydney, Australia Purpose/Objective: Patients managed with trimodal therapy (TMT) for muscle-invasive bladder cancer (MIBC) remain at risk of intravesical recurrences. Existing literature comparing outcomes between dose escalation and standard radiotherapy for MIBC remains limited, and the results are conflicting1-3. This retrospective analysis evaluates the efficacy and safety of dose escalation compared with standard-dose radiotherapy, with differentiation between invasive and non-invasive local control. Material/Methods: A multicentre retrospective analysis was conducted on patients with MIBC who underwent TMT with contemporary radiotherapy techniques from 2015 to 2025. In the standard dose cohort, the prescribed radiation regimens consisted of either 55Gy in 20 fractions or 64 Gy in 32 fractions to the entire bladder. For the dose-escalation group, a simultaneous integrated boost approach was undertaken to deliver up to 60 Gy in 20 fractions or 70 Gy in 32 fractions. The boost volume was delineated by contouring the gross tumour on CT, followed by a 5mm isotropic expansion to create the PTV (Diagram 1). The effect of dose escalation compared with standard dose on 2-year local control for invasive and non-invasive disease, metastasis-free survival, overall survival, bladder preservation, and toxicity was investigated. The survival curves between the two groups were compared using the Kaplan-Meier method, and the differences in subgroups were assessed with the log- rank test. Univariate and multivariate analyses were conducted using Cox proportional hazards regression.
Diagram 1: CT simulation image of a dose-escalation plan, the GTV boost is delineated in dark green and PTV boost is in pink. Results: The cohort consisted of 107 patients with a median follow-up of 23 months. On multivariable analysis, dose escalation was significantly associated with improved local control of invasive disease (HR 0.21 [0.05, 0.90], p = 0.02) compared to standard dosing (Diagram 2). There were no differences in local control for non-invasive disease (p=0.9), metastasis-free survival (p=0.7) and overall survival (p=0.5). Both groups tolerated radiotherapy well, with no difference in grade 2 or greater genitourinary and gastrointestinal toxicity (p=0.8, p=0.9, respectively). No patients receiving dose escalation required salvage cystectomy for invasive disease recurrence, compared with two patients who received standard dosing.
Diagram 2: Local control (invasive) rates of the cohort Conclusion: Preliminary evidence suggests efficacy of dose escalation with good tolerability, high rates of bladder preservation, and potentially lower rates of invasive recurrences compared with standard dose radiotherapy. This study’s findings support the need for further prospective studies to evaluate dose escalation as a technique to maximise the efficacy of TMT. References: 1. Huddart R, Hafeez S, Griffin C, Choudhury A, Foroudi F, Syndikus I, et al. Dose-escalated Adaptive Radiotherapy for Bladder Cancer: Results of the Phase
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