Multicenter population-level analysis of systemic therapy use in metastatic or recurrent prostate cancer.

89 Background: Treatment (tx) options for metastatic prostate cancer (mPC) have advanced significantly. There is a need for data in prescribing patterns and real-world survival outcomes of new therapeutics. Methods: We conducted chart review on all consecutive patients (pts) diagnosed with any stage of PC between 2016-2017 in British Columbia, and only included pts with de novo metastasis or later recurrence. We performed descriptive statistics, univariate and multivariate analysis to examine overall survival (OS). Results: This study included 796 pts with either de novo metastatic (n=554, 69.6%) or recurrent PC (N=242; 30.4 %); 743 (93.3%) had metastasis by time of cutoff (Sep 1, 2022). Median age at diagnosis of mPC in all patients was 73 (range 45-98). 790 (99.2%) started ADT. 263 (35.4%) had additional line of tx started with ADT at mCSPC; 309 (38.8%) had 1st line tx started at mCRPC. 149 pts (18.7%) had testing for homologous repair defects (21 positive). Radiotherapy (RT) to prostate for mPC were given to 93 (11.6%). 307 (38.6%) received 1 line of tx; 181 (22.7%), 2; 128 (16.1%), 3 or more. 432 (54.3%) received >=1 androgen receptor-axis-targeted therapies (ARAT). At cutoff, 474 (59.5%) died; most (n=400; 84.4%) died of prostate cancer. Pts who only stayed on ADT or who stayed on 1 additional tx had better OS than who had more than 1 line (NR vs. 55.5m vs. 21.0m, p=0.03). Similarly, pts who required no ARAT or stayed on 1 ARAT had longer OS than patients who had more than 1 ARAT (NR vs. 48.5m vs. 22.5m, p=0.009). No statistical difference in OS was seen between pts who had chemotx vs none, or pts on trial vs none. None of age, PSA at metastatsis, Gleason score, ADT type, RT to prostate or number of systemic tx were identified as an independent factor affecting OS on multivariate analysis. Pts with comorbidities (hypertension, CHF, diabetes, seizure, prior stroke, CAD or dementia) received abiraterone/prednisone, enzalutamide or apalutamide at a similar rate. Conclusions: Our multicenter data show low uptake of early treatment intensification in pts with mPC. Similar to other real-world data to date, pts who required less switch to another systemic tx were associated with better OS. Different ARATs were prescribed despite potential side effects at a similar rate to pts with major comorbidities.