Evaluation of de novo oligometastatic, oligorecurrent, and oligoprogressive prostate cancer patients managed with radiation therapy: A multi-institution, real-world dataset.

5099 Background: Oligometastatic prostate cancer (omPCa) is historically defined as ≤5 metastases, with non-standard treatment approaches and unknown prevalence in the molecular diagnostic imaging (MDI) era. Clinical trials in advanced PCa based on conventional imaging modalities (CIM) complicate extrapolation of findings to omPCa detected by MDI. We evaluated outcomes of omPCa patients (pts) treated with radiotherapy (RT) in a multi-institutional cohort. Methods: Pts presenting with de novo (synchronous), oligorecurrent (OR, metachronous), or oligoprogressive (OP, progressive) omPCa (<5 non-visceral lesions), detected by CIM and/or MDI and treated with RT across 7 institutions were identified. RT was metastasis-directed (MDT) only (or in the case of de novo pts, prostate-only or prostate + MDT) using conventional, hypofractionated or stereotactic body RT (SBRT) regimens. Clinical outcomes, including disease (dz) progression (any biochemical recurrence or distant metastasis, DM) and survival were assessed. Progression-free survival (PFS), DMFS, and overall survival (OS) were determined using the Kaplan-Meier method; univariable analyses were performed with Cox proportional hazard regression. Results: 625 omPCa pts (193 de novo, 342 OR, 90 OP) received RT between 2014-2024. Most pts (415/625, 66%) were diagnosed using MDI. 25% presented with pelvic lymph nodes (LNs) only, 7% non-regional LNs only, 56% bone-only dz, and 12% with a combination. Most pts (551/625) received systemic therapy with RT: 51% androgen deprivation therapy (ADT) alone, 43% ADT + androgen receptor signaling inhibitor (ARSI, n=239), and 6% ADT + ARSI + docetaxel. Median FU post-omPCa diagnosis was 26 months (range, 1-225) for 613 pts with details available. 153 pts developed new DM (outside of documented OM). Five-year OS post-diagnosis was 87% (95%CI 81,91). 5-year PFS post-RT was 34% (95%CI 24,44), with median PFS of 43 months. Concurrent ARSI use improved PFS (HR 0.67, 95%CI 0.50,0.91, p=0.01) on Cox proportional hazard regression. Use of any systemic therapy improved DMFS (HR 0.46, 95%CI 0.29,0.72, p<0.001). Both OR and OP dz were associated with worse DMFS (HR 2.2, 95%CI 1.4,3.5; HR 6.3, 95%CI 3.7,10.6, respectively, p<0.001 for both) and OP dz was associated with poor OS (HR 5.8, 95%CI 2.7,12.7). There was no impact by RT approach on outcomes. Conclusions: In this multi-institutional omPCa cohort reflecting real-world practice patterns of detection and treatment, the addition of ARSI to RT improved PFS, and use of any systemic therapy with RT improved DMFS. De novo omPCa had more favorable clinical outcomes compared to OP/OR presentations. Characteristic Age Gleason score Number of lesions Median (range) Score n (%) # n (%) 70 (44-92) 6 78910n/a 43 (7%)206 (33%)163 (26%)166 (27%)20 (3%)27 (4%) 12-34-5 351 (56%)229 (37%)45 (7%)