S1142
Clinical - Urology
ESTRO 2026
beyond posterior, lateral and posterolateral borders, indicating potential areas for refinement. Incorporation of PSMA PET/CT data into CTV delineation may improve robustness and reduce the risk of geographic misses in sRT. Keywords: PSMA PET/CT, local recurrence
Purpose/Objective: Accurate clinical target volume (CTV) delineation is crucial for effective salvage radiotherapy (sRT) following radical prostatectomy (RP). Current delineation guidelines are largely based on expert opinion and conventional imaging, with limited incorporation of prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) data. As PSMA PET/CT enables sensitive detection of local recurrences (LR), this study aims to evaluate the benefit of implementing PSMA PET/CT imaging into CTV delineation guidelines by evaluating spatial distribution of PSMA PET/CT positive LR and their coverage by five commonly used guidelines. Material/Methods: We retrospectively analyzed 77 post-prostatectomy patients with 79 LR, treated with sRT between 2014 and 2023. Planning CT-scans on which the LR were delineated as gross tumor volume (GTV) were further analyzed. The GTVs were mapped into a standard patient using a modified three-dimensional prostate bed template according to the PERYTON study. Coverage of five commonly used CTV guidelines, namely The Groupe Francophone de Radiothérapie Urologique (GFRU), the European Society for Radiotherapy and Oncology – Advisory Committee on Radiation Oncology Practice (ESTRO-ACROP), the PERYTON, the Faculty of Radiation Oncology Genito- Urinary Group (FROGG) and the Radiaton Therapy Oncology Group (RTOG) was assessed. Coverage was categorized as fully (100% coverage), partially (100%<coverage>0%) or not covered (0% coverage). Results: Most LR occurred in the vesicourethral anastomotic region (52/79, 66%) and predominantly (73/79, 92%) posterior to the midline of the bladder. Full coverage of LR varied across guidelines: RTOG (44/79, 56%), PERYTON (41/79, 52%), ESTRO-ACROP (34/79, 43%), GFRU (31/79, 39%), and FROGG (30/79, 38%). Partial coverage accounted for the remaining cases, except for one lesion each missed entirely by FROGG, GFRU, and PERYTON. The posterior, posterolateral, and lateral borders were the most frequent sites where recurrences exceeded guideline-defined CTVs.
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PSMA PET/CT–Directed Salvage Radiotherapy: Five- Year Outcomes in Patients with Local Recurrence versus PET-Negative Disease Erik Moar 1 , Michael Keilholz 2 , Gabriel T Sheikh 3 , Rudolf A Werner 3 , Christian Trapp 2 , Jozefina Casuscelli 4 , Sarah Frederike Brose 2 , Chukwuka Eze 2 , Franziska Walter 2 , Claus Belka 2,5 , Minglun Li 2,6 , Paul Rogowski 2 , Nina- Sophie Schmidt-Hegemann 2 1 Deparment of Radiation Oncology, LMU University Hospital, Munich, Germany. 2 Department of Radiation Oncology, LMU University Hospital, Munich, Germany. 3 Department of Nuclear Medicine, LMU University Hospital, Munich, Germany. 4 Department of Urology, LMU University Hospital, Munich, Germany. 5 Partner site Munich, Bavarian Cancer Resaerch Center (BZKF), Munich, Germany. 6 Deparment of Radiation Oncology, Lueneburg Hospital, Lueneburg, Germany Purpose/Objective: Up to 40% of radical prostatectomy patients experience biochemical recurrence (BCR). In this setting, salvage radiotherapy (sRT) is a curative treatment option, with better biochemical recurrence free survival (BRFS) rates when applied at lower prostate specific antigen (PSA) values. Prostate specific membrane antigen (PSMA) positron emission/computed tomography (PET/CT) has excellent recurrent tumor detection in low PSA values and PSMA PET/CT guided sRT has shown improved outcome compared to sRT alone. However, long term outcome data is still scarce and therefore this analysis aimed to evaluate long term treatment response for PSMA PET/CT guided sRT. Material/Methods: We retrospectively included 128 patients with BCR (PSA increase from postoperatively undetectable PSA) or biochemical persistence (BCP, i.e. postoperative PSA ≥ 0.1 ng/ml) who underwent PSMA PET/CT between 2014 and 2023 and subsequently received sRT to the prostatic fossa. Findings were categorized as PET- negative (miT0N0M0) or PET-positive (miTrN0M0), with dose escalation applied for local recurrences (LR). Patients were considered free of androgen deprivation therapy (ADT) influence if ≥ 6 months had passed since last application. Primary endpoint was biochemical recurrence-free survival (BRFS, PSA ≤ nadir + 0.2 ng/ml) and secondary endpoint was distant
Conclusion: PSMA PET/CT revealed that most LR after RP occur in the vesicourethral anastomotic region. Although current CTV guidelines achieve acceptable overall coverage, especially concerning the inferior, anterior and superior border, recurrences tend to extend
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