Prognostic clinical indicators in patients with metastatic castration-resistant prostate cancer treated with radium-223 plus enzalutamide: Data from patients in J-RAP-BSI trial.

OBJECTIVE

To investigate clinical factors associated with prognosis in patients with metastatic castration-resistant prostate cancer (mCRPC) and bone metastases treated with radium-223 dichloride (223Ra) and enzalutamide combination therapy.

SUBJECTS AND

METHODS

This retrospective study included a cohort of 71 mCRPC patients in Japan who underwent combination therapy with 223Ra and enzalutamide at 14 hospitals and had pretreatment bone scintigraphy findings available for analysis. Associations of overall survival (OS) with clinicopathological factors, including Eastern Cooperative Oncology Group (ECOG) performance status, hemoglobin, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), prostate-specific antigen (PSA), PSA doubling time, automated bone scan index (aBSI), and previous chemotherapy history, were assessed using the Cox proportional hazards model and log-rank testing.

RESULTS

Sixty (84.5%) of the 71 patients enrolled completed six cycles of 223Ra. The mean follow-up period was 21.9 months (range, 3.9-62.9 months), during which 35 patients (49.3%) died. Univariate analysis demonstrated that low hemoglobin (<12g/dL, P<0.0001), high PSA (≥20ng/mL, P<0.0001), ALP above the normal range (P=0.0067), and high aBSI (≥2.0%, P=0.0006) were significantly associated with shorter OS. In multivariable analysis, low hemoglobin [hazard ratio (HR) 5.52, 95% confidence interval (CI) 2.32-14.2, P<0.0001] and high PSA (HR 3.06, 95% CI 1.07-9.78, P=0.037) were identified as significant prognostic factors for OS.

CONCLUSION

In patients with mCRPC treated with 223Ra and enzalutamide combination therapy, pretreatment hemoglobin and PSA levels may serve as useful surrogate biomarkers for predicting overall survival.