S1245
Clinical - Urology
ESTRO 2026
were treated with short-course ADT (3-6 months) and SBRT (35-36.25 Gy) at Georgetown University Hospital. Patients received either leuprolide (n=166) or relugolix (n=115). Median age was 72 years, and 42% percent of patients were non-white. At baseline, 9.8% of men reported mild gynecomastia symptoms, while 2.2% experienced moderate to severe symptoms. The incidence of mild symptoms peaked at 15.4% at 6 months before declining to below baseline by 24 months. Moderate to severe symptoms reached the highest incidence of 5.8% at 12 months and decreased to 0% at 24 months, with a cumulative incidence of 10.3%. The development and resolution of gynecomastia fluctuated at various time points. There was no significant difference in symptoms between patients treated with leuprolide versus relugolix. Testosterone recovery (> 230 ng/dL) occurred in approximately 65% of patients by 12 months in those with follow-up.
of Cancer Research and The Royal Marsden NHS Foundation Trust, London, United Kingdom
Purpose/Objective: Bladder MRI-guided radiotherapy (MRIgRT) utilises online adaptive radiotherapy to refine target volumes and reduce irradiation of normal tissue [1,2]. This study reports the feasibility of a 0.5cm isotropic planning target volume (PTV) in whole-bladder MRIgRT (55.0Gy in 20 fractions), with a personalised approach
to margin expansion. Material/Methods:
Patients were instructed to not drink for two hours and empty their bladder prior to treatment. Following setup, a daily MRI (MRSESS) was acquired and adaptive (adapt to shape) workflow applied [2]. A verification MRI assessed need for a plan shift correction (adapt to position, ATP) [2]. A post-treatment MRI was acquired during delivery (MRPOST). Time from MRSESS to MRPOST was recorded. Offline, MRSESS and MRPOST were visually compared weekly, intra- fractional change was escalated to radiation oncologists. At their discretion, PTV margin personalisation was applied online and the adaptive plan used as a reference plan for subsequent fractions. Retrospectively, MRSESS structures were propagated to MRPOST images, clinical target volumes (CTV) re-edited, and the online adaptive plan recalculated (Monaco, Elekta AB, Stockholm, Sweden). CTV coverage was deemed acceptable if mandatory objective, V52.25Gy>95% was achieved. Where the CTV optimal objective, V52.25Gy>98%, was missed, the gross tumour volume (GTV) was delineated and dose reported. Results: 95 fractions from 5 patients were reported. PTV margins were personalised for 3 patients on fractions 9-10: 2 patients to 0.8cm anisotropic superiorly, and 1 patient to 0.8cm in all directions and 1.0cm posteriorly. ATP frequency median (range) was 4.5 (3- 5) per treatment course. Excluding patient 4, who required 18 ATP’s due to atypical bowel motion. Median (interquartile range) time (MRSESS to MRPOST) was 26.9 (22.0-33.4) minutes.84 MRPOST images were available for analysis. CTV coverage was acceptable in 93% (78/84) of fractions. Optimal and mandatory CTV coverage was missed in 15% (13/84) and 7% (6/84) of fractions respectively, however GTV coverage was acceptable in 84% (16/19) of these cases (Graph 1).
Conclusion: Bothersome gynecomastia occurs at low rates in men treated with neoadjuvant ADT.Gynecomastia symptom resolution occurs in most patients within two years after treatment. The temporary nature of gynecomastia incidence and severity may be important to include in patient counseling surrounding hormone therapy side effects. Keywords: prostate cancer, SBRT, ADT Feasibility of reducing PTV margins in whole bladder magnetic resonance image-guided adaptive radiotherapy: a personalised approach Bethany Williams 1 , Saleh Sandoughdaran 1 , Trina Herbert 1 , Robert Huddart 1,2 , Adam Mitchell 3 , Simeon Nill 3 , Shaista Hafeez 1,2 , Helen A McNair 1,2 1 Radiotherapy, The Royal Marsden NHS Foundation Trust, London, United Kingdom. 2 Oncology, The Institute of Cancer Research, London, United Kingdom. 3 Physics, The Joint Department of Physics, The Institute Digital Poster 3028
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