Prognostic factors of oncologic outcomes in metastatic chemotherapy-naïve castration-resistant prostate cancer treated with enzalutamide in actual clinical practice in East Asia.

OBJECTIVES: We aimed to evaluate the prognostic factors for chemotherapy-naïve castration-resistant prostate cancer (CRPC) treated with enzalutamide in actual clinical practice using easily accessible clinical variables.

METHODS AND MATERIALS: We retrospectively reviewed the following data from 113 patients with chemotherapy-naïve CRPC treated with enzalutamide: serum levels of prostate-specific antigen (PSA), testosterone, hemoglobin, total protein, albumin, and alkaline phosphatase (ALP); platelet, neutrophil, and lymphocyte counts; neutrophil-to-lymphocyte ratios (NLRs); and liver profiles. PSA progression-free survival (PFS), radiological PFS, and overall survival were estimated by Cox regression analysis.

RESULTS: Compared with baseline levels, laboratory values at 2 months showed significantly lower PSA (160.2 ± 351.5 ng/ml vs. 47.4 ± 117.1 ng/ml) and ALP levels (201.86 ± 223.77 IU/l vs. 148.25 ± 146.81 IU/l) and a significantly higher percentage of lymphocytes (28.1% ± 10.6% vs. 31.2% ± 9.7%); those at 1 month showed a significantly lower percentage of neutrophils (61.0% ± 11.0% vs. 57.1% ± 12.5%). In the multivariate analysis, poor prognostic factors for PSA PFS were Gleason score ≥ 9 (hazard ratio [HR] 2.022; P = 0.0250); visceral metastasis (HR 3.143; P = 0.0002); high NLR (HR 1.205; P = 0.0126); and high ALP (HR 1.002; P = 0.0015). For radiological PFS, high NLR (HR 1.249; P = 0.0002) and high ALP (HR 1.002; P = 0.0001) were associated with poor outcomes. The predictors of poor overall survival were visceral metastasis (HR 3.155; P < 0.0001); high NLR (HR 1.341; P < 0.0001); and high ALP (HR 1.001; P = 0.0017).

CONCLUSION: Enzalutamide is less effective in patients with metastatic chemotherapy-naïve CRPC with Gleason scores ≥ 9, visceral metastasis, high NLR, and high ALP.