Introduction: We aimed to investigate several clinical and biochemical parameters, including palliative external beam radiation therapy (EBRT) to predict survival in patients with metastatic castrate-resistant prostate cancer (mCRPC) treated with radium-223 (223Ra).
Methods: We tested known and possible prognostic parameters, including palliative EBRT, both prior and concurrent to 223Ra. Logrank test (Kaplan-Meier method) and Cox regression analysis were used to predict overall survival (OS).
Results: A total of 133 patients were treated with 223Ra; median age was 72 years. Median OS was 9.0 (95% confidence interval [CI] 7.4-10.6) months. By univariate analysis (log-rank test), baseline Eastern Cooperative Oncology Group performance status (ECOG PS) 0-1 (p=0.001), ≥5 cycles of 223Ra (p<0.001), baseline hemoglobin (Hb) ≥120 g/L (p <0.001), baseline total alkaline phosphatase (tALP) <110 U/L (p=0.001), and any prostate-specific antigen (PSA) decline at week 12 (p=0.013) were associated with increased OS. EBRT prior and/or concurrent to 223Ra showed a trend (p=0.051) towards inferior OS by univariate analysis only. By multivariate analysis, significant factors were PS 0-1 (hazard ratio [HR] 1.94, 95% CI 1.3-2.9, p=0.001), Hb ≥120 g/L (HR 0.5, 95% CI 0.3-0.9, p=0.011), and absence of docetaxel use prior to 223Ra (HR 1.86, 95% CI 1.08-3.22, p=0.026). With baseline Hb, tALP, and ECOG PS, we were able to divide patients into three groups with different median OS (months): 23.0 (95% CI 12.8-33.2), 8.0 (95% CI 6.7-9.3), and 5.0 (95% CI 3.1-6.9) for low-, intermediate-, and high-risk, respectively (p<0.001).
Conclusions: We found that 223Ra therapy can result in an OS of close to two years in carefully selected patients. Earlier administration of 223Ra therapy to fitter patients with mCRPC should be tested.