Real-World Utilization Of Radium-223 (Ra-223) For The Treatment Of Metastatic Castration-Resistant Prostate Cancer (Mcrpc): A Us Tertiary Oncology Center Analysis

223 Background: Guidelines for optimal sequencing of approved mCRPC therapies do not exist. This study evaluated treatment patterns and overall survival (OS) among patients (pts) with mCRPC treated with Ra-223 in an academic clinical setting. Methods: A retrospective chart review study was conducted at Dana-Farber Cancer Institute of bone metastases-predominant mCRPC pts treated with Ra-223. Treatment patterns from 2013-2018 were evaluated including Ra-223 initiation pre- vs. post-chemotherapy (chemo). OS was examined using Kaplan-Meier medians and 95% confidence intervals (CIs). Results: 220 pts were treated with Ra-223 (64 pre-chemo, 83 post-chemo, 73 no chemo). Median Ra-223 injections per pt was 6.0 and 5.0 in the pre- vs. post-chemo cohorts, respectively (p<0.001). Mean chemo cycles received was 9.0 (pre-chemo) and 9.2 (post-chemo); on average, Ra-223 was given in the 3rd and 5th mCRPC line of therapy (pre- and post-chemo, p<0.001). 41.8% of pts were treated with Ra-223 in combination (combo) with another mCRPC therapy, commonly abiraterone acetate (37.0%) or enzalutamide (44.4%). The majority received combo therapy for the duration of Ra-223 treatment. 17.6% started another agent after Ra-223 initiation; 17.6% initiated Ra-223 while on an established therapy. Median OS from Ra-223 initiation was 12.4 months (95% CI 10.2, 13.9). Median OS from first mCRPC treatment was slightly longer for pts with Ra-223 pre- vs. post-chemo (by 2 months) and for pts with Ra-223 combo vs. monotherapy (by 3 months). Conclusions: Ra-223 improves OS in mCRPC, and longest OS was seen in those with Ra-223 pre-chemo. Retrospective analysis of 5 years of Ra-223 treatment data from an academic center demonstrates that pts treated pre-chemo on average obtained 1 additional cycle of Ra-223, subsequent chemo administration was not limited and OS measured from first mCRPC therapy was not significantly different.[Table: see text]