Radium-223 in the third-line setting in metastatic castrate-resistant prostate cancer (mCRPC): impact of concomitant use of enzalutamide on overall survival and predictors of improved overall survival

Abstract Introduction Radium-223 (Ra-223) has been recommended for bone-dominant metastatic prostate cancer (mCRPC). Second-generation hormone therapy (2nd HT) in combination with radium-223 in mCRPC has been utilized, yet its benefit has not been well elucidated. We investigate the potential survival benefit of concomitant enzalutamide with radium-223 in the third-line setting and predictors of improved overall survival (OS). Patients and Methods We retrospectively identified 51 patients with bone-dominant mCRPC that were treated with (Ra-223) in the post-chemotherapy and hormone therapy setting, either alone (Group A; n = 32) or with concomitant enzalutamide (Group B; n = 19). The primary endpoint was to study the overall survival difference between groups (A) and (B). The secondary endpoint was to identify predictors of improved OS with radium-223 in the third-line setting. Results Mean age was 70.9 years, median baseline prostatic specific antigen (PSA) was 23.1 ng/ml, Alkaline phosphatase (ALP) was 91 IU/L, and Hemoglobin (Hgb) concentration was 12.5 g/dl. There was no difference in median OS between group (A) and (B); 20.4 months versus 17.5 months for patients in group (A) and (B), respectively (p-value = 0.5186). In univariate and multivariate analyses, only pre Ra-223 PSA of Conclusion In our study cohort, concomitant use of enzalutamide with Radium-223 in the mCRPC setting was not associated with improved overall survival. Only pre-treatment PSA