The presence of lymph node metastases and time to castration resistance predict the therapeutic effect of enzalutamide for castration-resistant prostate cancer.

ABSTRACT

BACKGROUND: Enzalutamide is effective against castration-resistant prostate cancer (CRPC). However, it is unclear which patients would benefit more from enzalutamide treatment. Here, we analyzed patients who received enzalutamide as first-line therapy for CRPC and evaluated the factors that predict treatment response and prognosis. METHODS: We retrospectively analyzed 101 patients treated with enzalutamide for CRPC at our institution. As primary endpoints we regarded the prostate-specific antigen (PSA) response rate and PSA-progression-free survival (PSA-PFS) from the start of enzalutamide treatment. Laboratory and imaging data were analyzed to predict treatment efficacy. RESULTS: PSA reductions of ≥ 50% and ≥ 90% were observed in 78 (77%) and 47 (47%) patients, respectively, compared with the baseline. During the follow-up period, 67 (66%) patients showed PSA progression, with a median PSA-PFS of 11 months. Moreover, 31 patients (31%) died, with a median overall survival of 64 months. On multivariate analysis, lymph node metastases at the start of enzalutamide treatment [odds ratio (OR) 0.0575, 95% confidence interval (CI) 0.0105-0.316, p = 0.0010] and time to CRPC (OR 0.177, 95% CI 0.0428-0.731, p = 0.0167] were associated with ≥ 90% PSA response. Lymph node metastases (hazard ratio [HR] 3.00, 95% CI 1.48-6.09, p = 0.0023) and time to CRPC (HR 1.84, 95% CI 1.02-3.30, p = 0.0419) were also predictors of PSA-PFS on a multivariate model. CONCLUSIONS: Time to CRPC and lymph node metastasis were predictors of the PSA response rate and PSA-PFS.