ESTRO 2025 - Abstract Book

S2109

Clinical - Urology

ESTRO 2025

4208

Digital Poster THE VALUE OF COMPLETE RESPONSE IN OLIGOMETASTASIS-DIRECTED SBRT FOR PROSTATE CANCER: A MONOINSTITUTIONAL EXPERIENCE Marco Lucarelli 1 , Giulia de Pasquale 1 , Rosario Bonelli 1 , Antonietta Augurio 1 , Annamaria Vinciguerra 1 , Consuelo Rosa 1 , Andrea D'Aviero 1,2 , Domenico Genovesi 1,2 1 Department of Radiation Oncology, "S.S. Annunziata" Hospital, Chieti, Italy. 2 Department of Medical, Oral and Biotechnological Sciences, “G. D’Annunzio” University of Chieti, Chieti, Italy Purpose/Objective: The role of Stereotactic Body Radiotherapy (SBRT) for prostate cancer oligometastases has been validated in several experiences, with low toxicities rates and high patients’ compliance. We conducted a monoinstitutional analysis evaluating the impact of complete response on the outcomes of patients treated with SBRT for prostate oligometastases. Material/Methods: From 2019 to 2024, we retrospectively analyzed 30 prostate cancer patients, with up to five lymph-nodal oligometastases with ongoing systemic therapy or naïve for Androgen deprivation therapy. Toxicities were registered following RTOG Scale. Local Control (LC), Disease-free Survival (DFS) and Overall Survival (OS)were analyzed. According to post-SBRT imaging evaluation, patients were sub-grouped in complete responders (CRs) and not-complete responders (Not-CRs). Results: The median age was 71 years (range: 50 – 15). Among the 30 patients, 21 were treated for lymph nodal oligometastases and 9 for bone oligoprogressive lesions. The median PSA prior to SBRT was 2,4 ng/mL (range: 0.3 – 13.7 ng/mL). Patients received SBRT with median total dose of 30 Gy (range: 24 – 40 Gy) in a median number of 5 (range, 3 – 5) fractions. The treatments were administered on alternate days in 25 (80%) patients. The median follow up was 25 months (range: 6 – 60 months). LC rates were 93%, 80% and 80% at 1, 2 and 3 years. PFS rates were 76%, 50% and 46% at 1, 2 and 3 years. Three patients developing a sequential oligometastatic disease underwent a second SBRT course. OS rates were 93%, 80% and 80% at 1, 2 and 3 years respectively. The subgroups analysis considering CRs and Not-CRs, we observed statistical significance in terms of OS (p=0.03) with 1-, 2- and 3- year rates of 100%, 92% and 91% for CRs versus 1-, 2- and 3- year rates 75%, 65% and 65% for Not-CRs (Fig.1). Higher LC rates were shown in CRs subgroup with 93% at 1, 2 and 3 years compared to 74%, 64% and 64% at 1, 2 and 3 years in Not-CRs subgroup (p=0,14). No G3 or higher adverse events were reported.