Impact of synchronous (sync) vs metachronous (meta) metastasis at the presentation on survival in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) treated with androgen receptor signaling inhibitors (ARSIs).

Abstract

5049 Background: Pts with sync metastatic castration-sensitive prostate cancer (mCSPC) appear to have worse survival outcomes and earlier time to developing castration resistance than pts with meta mCSPC (PMID: 33914595). However, the impact of the initial timing of metastasis on survival in the mCRPC setting is less clear. Herein, our objective was to assess the correlation between the sync/meta metastatic disease presentation and survival in real-world newly diagnosed mCRPC pts. Methods: In this IRB-approved study, patient-level data were collected retrospectively. Eligibility: confirmed diagnosis of mCRPC, treatment with ARSI (abiraterone or enzalutamide) as first-line (1L) therapy for mCRPC, and no prior exposure to ARSI in the mCSPC or localized states. The disease was considered sync if distant metastasis was diagnosed within 90 days of the initial prostate cancer diagnosis. Study endpoints: progression-free survival (PFS) was defined from the start of therapy for 1L mCRPC to progression (per PCWG-2) or death from any cause. Overall survival (OS) was defined from the start of therapy for 1L mCRPC to the date of death from any cause or censored at the last follow-up. A multivariate analysis using the Cox proportional hazards model was used, adjusting for potential confounders. Results: 323 pts (144 sync and 179 meta) were eligible and included in the analysis. Sync and meta pts had respectively similar baseline characteristics: median PSA (19.6 vs 20.8 ng/ml), liver metastasis (9 vs 12.3%), median alkaline phosphatase (97 vs 95 IU/L), and ECOG performance > 1 (9 vs 3.9%). The difference in median PFS was not statistically significant (8.2 vs. 10.7 months, HR 1.13, 95% CI 0.85-1.49, p=0.4 for sync and meta, respectively). Median OS was significantly shorter in pts with sync compared to meta (26 vs. 38.7 months, HR 1.51, 95% CI 1.11-2.08, p=0.01). In the multivariate analysis, the initial timing of metastasis remained an independent prognostic factor. Conclusions: For the first time, we report the impact of the initial timing of metastasis on mCRPC prognosis in a real-world patient population with sync disease being associated with having a poor prognosis. Initial timing of metastasis may be worth accounting for in future mCRPC clinical trials to explore its prognostic value further. These hypothesis-generating data need external validation. [Table: see text]