Predictive factors of survival outcomes in first-line therapy for metastatic castration-resistant prostate cancer

Objectives: To investigate predictive factors of survival of metastatic castration-resistant prostate cancer patients undergoing first-line treatment with androgen receptor pathway inhibitors or docetaxel. Methods: Japanese patients with metastatic castration-resistant prostate cancer treated with androgen receptor pathway inhibitor or docetaxel between 2008 and 2018 were included. The differential impact of various clinicopathological factors on the outcome, including progression-free survival and overall survival, was compared between treatment with androgen receptor pathway inhibitor and docetaxel. Results: Of 254 patients with metastatic castration-resistant prostate cancer, 119 (46.9%) and 135 (53.2%) were treated with androgen receptor pathway inhibitor and docetaxel, respectively. The multivariate analysis showed that androgen receptor pathway inhibitor was an independent prognostic factor for better progression-free survival (hazard ratio 0.62, 95% confidence interval 0.42–0.92, P = 0.016) and overall survival (hazard ratio 0.61, 95% confidence interval 0.41–0.93, P = 0.021), compared with docetaxel. Pretreatment prostate-specific antigen levels and time to castration-resistant prostate cancer were differentially associated with progression-free survival and overall survival between androgen receptor pathway inhibitor or docetaxel. In patients who presented <6 months to castration-resistant prostate cancer, progression-free survival was shorter in those treated with androgen receptor pathway inhibitor (median 1.1 months, 95% confidence interval 0.2–2.8 months) compared with those who received docetaxel (median 5.0 months, 95% confidence interval 1.8–6.7 months; P = 0.014). Conclusions: First-line therapy with androgen receptor pathway inhibitor is associated with a better prognosis when compared with docetaxel, even after adjustment for prognostic factors. However, a shorter time to castration-resistant prostate cancer is associated with better progression-free survival for patients receiving docetaxel, suggesting that docetaxel is the preferred option for patients with a shorter time to castration-resistant prostate cancer.