Correlation of baseline testosterone (T) level with survival outcomes in patients (Pts) with metastatic hormone-sensitive prostate cancer (mHSPC): Analysis of patient (pt)–level data from SWOG 1216 study.

5096 Background: Retrospective data suggest that low baseline serum T may be associated with inferior survival outcomes in mHSPC [PMID: 38444678]. Whether this relationship persists in rigorously controlled, randomized clinical trial populations remains unclear. We examined the prognostic impact of baseline T using patient-level data from the phase 3 SWOG 1216 trial which randomized pts with mHSPC in 1:1 to ADT + bicalutamide (standard arm) or ADT + orteronel (experimental arm). Methods: Patients treated on SWOG 1216 trial with available baseline T levels were eligible and included in this secondary analysis. Baseline T was summarized by median (IQR) and dichotomized at the median as ≤ median vs > median. Overall survival was the primary endpoint; progression-free survival (PFS) and prostate-specific antigen (PSA) response were secondary endpoints. PSA response rates were divided into complete response (CR; PSA <0.2 ng/mL), partial response (PR; PSA between 0.2 and 4.0 ng/mL), and no response (NR; PSA >4.0 ng/mL) at a 7-month landmark following randomization. OS and PFS were estimated by Kaplan-Meier within each arm, with median survival (95% CI) and number of events reported. Comparisons were performed using the log-rank test. PSA response was summarized as n (%), and groups were compared using Pearson’s chi-squared test. All tests were two-sided with alpha = 0.05. Results: Of 1279 pts, 218 pts had baseline T levels. Median T level was 312.5 ng/ml (IQR 89.25 - 462 ng/ml). In both experimental and standard arms, there was no significant difference in OS, PFS, or PSA response between patients with baseline T levels above vs below the median (Table). Similarly, in both arm, there was no difference in outcomes based on baseline T levels grouped by quartiles, as well as baseline T levels as a continuous variable (data will be presented at the conference). Conclusions: In this patient-level analysis of a phase 3 trial, there was no statistically significant association between baseline T and outcomes in mHSPC. Based on these data, baseline T may not be used for prognostication or treatment selection in patients receiving systemic therapy in mHSPC. Limitations include a small sample size. These hypothesis-generating data require external validation before clinical application. Treatment Arm T Level OS Median (95% CI), months N (events) P-value PFS Median (95% CI), months N (events) P-value PSA complete response n (%) PSA partial response n (%) No PSA Response (%) P-value Experimental ≤ Median 63 (47, NR) 71 (37) 0.11 30 (20, 64) 71 (49) 0.11 37 (50%) 18 (60%) 16 (62%) 0.5 > Median NR (68, NR) 59 (22) 57 (26, NR) 59 (30) 37 (50%) 12 (40%) 10 (38%) Standard ≤ Median 72 (45, NR) 38 (20) 0.7 19 (12, 34) 38 (29) 0.9 14 (42%) 9 (45%) 15 (43%) >0.9 > Median 57 (43, NR) 50 (22) 19 (13, 35) 50 (39) 19 (58%) 11 (55%) 20 (57%)