Association of baseline characteristics with adverse events (AEs) in the PROpel trial of olaparib (ola) plus abiraterone (abi) as first-line (1L) treatment for metastatic castration-resistant prostate cancer (mCRPC).

Abstract

e17030 Background: The PROpel trial (NCT03732820) met its primary endpoint and showed a statistically significant radiographic progression-free survival benefit (hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.54–0.81; P<0.0001) with ola + abi vs placebo + abi in 1L mCRPC; whilst not statistically significant, overall survival (OS) was numerically prolonged (median 42.1 vs 34.7 months; HR 0.81, 95% CI 0.67–1.00; P=0.0544). To further inform clinical decision making, we provide exploratory post hoc analysis investigating the relationship between selected patient baseline characteristics and AEs for ola + abi. Methods: Anemia and venous thromboembolism events (VTEs) were identified as the only grade (Gr) ≥3 AEs or AEs of special interest reported in >20 (>5.0%) patients (pts) in the ola + abi arm (data cutoff 12 Oct 2022). Baseline characteristics were correlated with AEs using Cox regression by backwards elimination and analysis with AEs as dependent variables. Baseline characteristics assessed included: age (<70 or ≥70 y), time since diagnosis (<median or ≥median) , ECOG status (0 or 1), metastatic sites (visceral [yes or no], bone only [yes or no]), number of bone metastases (0, 1–4, 5‒9, 10‒20 or >20), Gleason score (<9 or 9–10), homologous recombination repair mutation status (HRRm, non-HRRm or unknown), race (white or non-white), prior docetaxel at metastatic hormone-sensitive prostate cancer (yes or no), pain (symptomatic or asymptomatic/mildly symptomatic), type of progression (prostate-specific antigen [PSA], radiographic or both), prior radiotherapy (yes or no) and albumin, creatinine, lactate dehydrogenase, alkaline phosphatase (ALP), hemoglobin (10<12 or ≥12) and log PSA levels. Results: 398 pts received ola + abi. 64 (16.1%) had Gr ≥3 anemia and 34 (8.5%) a VTE. Baseline characteristics correlated significantly with increased risk of these AEs as shown (Table); characteristics not shown were not associated with AEs. Conclusions: These results provide insight into which baseline characteristics correlate with the risk of Gr ≥3 anemia. Pts with abnormal ALP, pre-existing anemia, ECOG PS 1 or age ≥70 years could be at higher risk and the development of Gr ≥3 anemia during treatment with ola + abi should be monitored. Clinical trial information: NCT03732820 . [Table: see text]