Effects of six-cycle completion and earlier use of radium-223 therapy on prognosis for metastatic castration-resistant prostate cancer: A real-world multicenter retrospective study

•We evaluate the effect of 6-cycle completion and earlier use of radium-233 dichloride (Ra223) on the prognosis of patients with metastatic castration-resistant prostate cancer (mCRPC)•We retrospectively evaluated 75 patients with bone metastases-predominant mCRPC who were treated with Ra223 to assess the effect of Ra223 completion (6 cycles) on patient prognosis, and the factors associated with Ra223 incompletion (fewer than 6 cycles).•We found unfavorable performance status (>0), prostate-specific antigen (PSA) level >10 ng/ml, and Ra223 incompletion were significantly associated with poor overall survival.•Unfavorable factors (EOD 3–4 and ≥3 prior treatments) were significantly associated with Ra223 incompletion.•Six-cycle completion and earlier administration of Ra233 are potentially associated with favorable survival.