The prognostic superiority of second-generation androgen receptor signaling inhibitor in patients with non-metastatic castration-resistant prostate cancer

Objective: The aim of this study was to compare prognostic outcomes of administering first- or second-generation androgen receptor signaling inhibitors in non-metastatic castration-resistant prostate cancer and to find prognostic indicators. Methods: This retrospective study included 198 patients with non-metastatic castration-resistant prostate cancer from 14 institutions associated with Tokai Urologic Oncology Research Seminar. Forty-two patients were treated with combined androgen blockade using first-generation inhibitors (bicalutamide or flutamide), and 156 were treated with second-generation inhibitors (abiraterone/enzalutamide or apalutamide/darolutamide) after primary androgen deprivation therapy failure. We compared survival outcomes of combined androgen blockade using first-generation inhibitors and second-generation inhibitor treatments, and analyzed clinicopathological or serum parameters and survival outcome. Results: Combined androgen blockade and second-generation androgen receptor signaling inhibitor groups demonstrated median progression-free survival of 10.2 (95% confidence interval: 5.5–12.3) and 26.0 (95% confidence interval: 21.9–38.4; P < 0.001) months, respectively. Cut-off levels for clinical biomarkers were targeted to <0.2 ng/ml prostate-specific antigen levels 3 months after treatment initiation for non-metastatic castration-resistant prostate cancer; the patient group that achieved this showed better progression-free survival (median 14.7 months, 95% confidence interval: 10.3–23.9 not achieved, median not applicable, 95% confidence interval: 24.6–not applicable achieved; P < 0.00001). Multivariate analysis revealed significant prognostic factors: second-generation androgen receptor signaling inhibitor as first-line treatment (odds ratio: 5.05, 95% confidence interval: 1.54–16.6) and a high hemoglobin level (odds ratio: 2.92, 95% confidence interval: 1.26–6.76). Conclusions: Our findings suggested prostate-specific antigen < 0.2 ng/ml after 3 months may be a practical prognostic indicator of survival outcomes in non-metastatic castration-resistant prostate cancer. Patients showing a high hemoglobin level should be intensively treated with second-generation androgen receptor signaling inhibitors rather than combined androgen blockade using first-generation inhibitors.