PSA time to nadir as a prognostic factor of first-line docetaxel treatment in castration-resistant prostate cancer: Multicenter validation in patients from the Chinese Prostate Cancer Consortium.

Objective: Docetaxel-based chemotherapy remains the first-line treatment for patients with metastatic castration-resistant prostate cancer (mCRPC) in China. We have previously shown that time to nadir (TTN) of prostate-specific antigen (PSA) is an important prognostic factor in patients from a single center in Northwestern China. In this study, we performed a multicenter validation of the prognostic role of TTN in additional Chinese patients with mCRPC receiving docetaxel treatment. Materials and Methods: The data were gathered from 170 eligible Chinese patients who received docetaxel chemotherapy from January 2007 to October 2018 in 11 Chinese Prostate Cancer Consortium member hospitals in China. TTN was defined as the time from start of chemotherapy to the nadir of PSA level during the treatment. Multivariable Cox regression models and Kaplan-Meier analysis were used to predict overall survival (OS) and progression-free survival (PFS). Results: Patients with a TTN ≥ 15 weeks had a longer OS and PFS compared to those with a TTN < 15 weeks (43 vs. 15 months, P < 0.001; 24 vs. 6 months, P < 0.001, respectively). In addition, Patients with a TTN ≥ 15 weeks and PSA nadir <4.55ng/ml were associated with longer OS than others (HR 0.093, 95% CI 0.044-0.188, P < 0.001; HR 4.002, 95% CI 1.890-8.856, P = 0.001, respectively) and TTN, PSA nadir, PSA baseline (optimal threshold 56.07 ng/ml), and PSA reduction (optimal threshold 50%) were associated with PFS (HR 0.238, 95% CI 0.149-0.382, P < 0.001; HR 1.676, 95% CI 1.033-2.722, P = 0.037; HR 1.770, 95% CI 1.134-2.763, P = 0.012; HR 0.573, 95% CI 0.428-0.756, P < 0.001; respectively). Furthermore, patients with a PSA nadir <4.55 ng/ml had longer OS and PFS compared to other patients when TTN was ≥15 weeks. Conclusion: In this multicenter validation study, TTN and PSA nadir remain important prognostic markers in predicting therapeutic outcomes in Chinese men who receive chemotherapy for mCRPC. [ABSTRACT FROM AUTHOR]