3304 - Outcomes of Oligorecurrent Prostate Cancer Treated with Metastasis Directed Therapy

Purpose/Objective(s): Historically, metastatic prostate cancer (Pca) has been treated with androgen deprivation therapy (ADT), which may cause side effects resulting in cessation of therapy. Oligometastatic prostate cancer (OMPca) is defined as =3-5 extraprostatic lesions. Metastasis directed therapy (MDT) has been shown to improve progressive free survival (PFS) and ADT free survival, however outcomes with combined modality therapy remain sparse. We present our outcomes of oligorecurrent prostate cancer treated with MDT with and without ADT.

Materials/Methods: This was a single institution retrospective review of patients with oligorecurrent (=5 lesions) prostate cancer from 2016-2023, in patients with localized disease (dz) at diagnosis staged with PSMA-PET or, for those with inadequate staging, at least six months (mo) after curative-intent treatment (RT or surgery), who then received MDT. All patients received stereotactic ablative radiotherapy (SABR) or elective nodal IMRT with a boost to the involved node. Time from primary treatment to oligorecurrent disease (ORD), use of ADT with MDT (Cohort A: No ADT; Cohort B: ADT), and time to radiographic progression were recorded. PFS was calculated by Kaplan Meier survival estimate.

Results: A total of 140 patients were included, with median follow up 25 mo (range 5-87 mo); 33% in Cohort A (n= 46) and 67% in Cohort B (n=94). Regarding primary treatment, the highest Gleason score and type of treatment delivered are listed in Table 1. Median time to ORD was 61 months and 59 months for Cohorts A and B, respectively, and 29% presented with N1, 14% M1a, 46% M1b, and 6% M1c dz. Seventy-eight percent had a single site of oligometastatic dz, 25% 2 sites, 2% 3 sites, and 1% with 5 sites. All patients received MDT (SABR n=113, IMRT n=27) and 19% received elective nodal RT. Median duration of ADT in cohort B was 23 mo (range: 2-84 mo). Cohort B had higher 2-year PFS compared to Cohort A (43% v 87% Log rank p < 0.001). Median freedom from progression in Cohort A was 18 months. On multivariate Cox analysis, use of ADT was significantly associated with higher PFS (HR 0.16, 95% CI [0.08-0.32], p<0.001); however, Gleason score (6-7 vs. 8-10), number of ORD (1 vs. >1), or time from diagnosis to ORD were not significantly associated.

Conclusion: In our investigation, patients with ORD treated with MDT alone were able to avoid systemic therapy for a median of 18 months. The combination of ADT with MDT can further improve PFS and is an emerging treatment paradigm for OMPca.