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e17067 Background: Androgen receptor signaling inhibitor (ARSIs) treatment (APA or ENZ), in combination with androgen deprivation therapy (ADT) has improved the prognosis of patients with de novo mCSPC. PSA decline ≥90% (PSA90) after ARSI initiation has been associated with improved survival and delayed disease progression. The objective of this study was to compare PSA90 response at 6-months among next-generation ARSI-naïve patients with de novo mCSPC initiating APA or ENZ. Methods: Clinical data for US community urology practices from PPS Analytics was linked with claims data from Komodo Health Solutions Research Database. Included patients were assigned to exclusive cohorts based on the first APA or ENZ dispensation or pharmacy claim on or after 12/16/2019 (index date). Patients were also included if they had de novo mCSPC, identified if a metastatic diagnosis was observed ≤180 days after the initial prostate cancer (PC) diagnosis, ≥12 months of pre-index clinical activity, and ≥1 PSA measurement within 13-weeks pre-index. Follow-up spanned from index date until the earliest of index ARSI discontinuation (i.e., gap ≥90 days supply) or switch, radiopharmaceutical initiation, or end of clinical activity/data availability (9/30/2022). Pre-index characteristics (i.e., age, race, region, payer type, index year, time from metastasis, time from PC diagnosis, prior use of ADT, first-generation antiandrogen, or chemotherapy, metastasis locations, most recent PSA and testosterone level, and earliest Gleason score) were balanced between cohorts using inverse-probability of treatment weighting (IPTW). PSA90 was defined as the earliest ≥90% decline in PSA relative to most recent pre-index PSA. The proportion of patients achieving PSA90 was compared using a weighted Kaplan-Meier analysis and the time-to-PSA90 response was compared using a weighted Cox proportional hazards model. Results: Overall, 332 APA and 383 ENZ patients were identified. Patients’ pre-index characteristics were balanced using IPTW (Table). By 6 months post-index, 81.0% of APA and 75.2% of ENZ patients had ≥1 PSA test. PSA90 response at 6 months was achieved by a significantly higher proportion of APA patients, as compared to ENZ patients (62.8% vs 49.6%; p=0.004; Table). Median time to PSA90 response was 3.5 months for APA and 6.1 months for ENZ. Conclusions: This study of RW US data showed that a greater percentage of patients with de novo mCSPC treated with APA achieved a deep, early PSA response by 6 months as compared to those treated with ENZ. Table: see text
Lowentritt et al. (Sat,) studied this question.