Treatment patterns in men with metastatic castration sensitive prostate cancer (mCSPC) in the United States (US).

e19131 Background: Given recent advances in treatment options for mCSPC, this study assessed US real-world treatment patterns of mCSPC patients over time. Methods: The Optum Clinformatics Extended DataMart was used to identify men with ≥2 claims for PC, ≥1 claim for metastasis, ≥1 castration sensitivity (CS) indicator (CS diagnosis code [dx]; castration and no prostate-specific antigen [PSA] rise; or hormone/castration naive for ≥18 months [mo] before metastasis). Index (idx) date was the 1 st metastasis dx date on or after 1 st PC dx and from 2015-2018. Patients were excluded if they had a pre-idx castration-resistance (CR) indicator (CR dx; castration within ≥90 days pre-idx or with PSA rise; or a claim for a drug solely recommended for metastatic CRPC). mCSPC period (F/U) was defined as time from idx until CR (i.e., any post-idx CR indicator or initiation of abiraterone acetate [ABI] or docetaxel [DOC] ≥12 mo after post-idx androgen deprivation therapy [ADT] initiation or ≥12 mo post-idx for those with no ADT) or end of data. mCSPC treatment patterns in F/U were assessed overall and in patients with idx years (yrs) in 2015-2016 and in 2017-2018, separately. Descriptive statistics were used: n (%) for binary and mean [SD] for continuous variables. Results: In the 2,825 mCSPC patients identified (age: 75 [9] yrs; F/U: 10.9 [9.0] mo), 43% were in the 2015/16 cohort (age: 75 [9] yrs; F/U: 15.8 [10.2] mo); and 57% were in the 2017/18 cohort (age: 75 [9] yrs; F/U: 7.2 [4.7] mo). The most common first-line (1L) mCSPC therapy was ADT only (Table), but patients in the 2017/18 cohort had fewer ADT only as 1L (43% vs. 52%) and more 1L ABI (10% vs. 4%) compared to the 2015/16 cohort. About 4% (2015/16: 5%; 2017/18: 3%) of patients received second-line (2L) mCSPC therapies, with ABI (74%) and DOC (25%) as the main 2L therapies observed. In patients receiving 2L mCSPC therapies, the 2017/18 cohort had more 2L ABI (81% vs. 68%) and fewer 2L DOC (19% vs. 30%) compared to the 2015/16 cohort. Conclusions: A large proportion of men with mCSPC were untreated/deferred treatment or were treated with ADT only, highlighting unmet needs in this patient group. As additional therapies for mCSPC become available, this trend is expected to improve, as supported by more recent treatment patterns. [Table: see text]