Docetaxel-based chemotherapy remains the first-line treatment for patients with metastatic castration-resistant prostate cancer (mCRPC) in China; however, the prognostic factors associated with effects in these patients are still controversial. In this study, we retrospectively reviewed the data from 71 eligible Chinese patients who received docetaxel chemotherapy from 2009 to 2016 in our hospital and experienced a reduction of prostate-specific antigen (PSA) level ≥50% during the treatment and investigated the potential role of time to nadir (TTN) of PSA. 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). In these patients, the median of TTN was 17 weeks. Patients with TTN ≥17 weeks had a longer response time to chemotherapy compared to TTN <17 weeks (42.83 vs 21.50 weeks, P < 0.001). The time to PSA progression in patients with TTN ≥17 weeks was 11.44 weeks compared to 5.63 weeks when TTN was <17 weeks. We found several factors to be associated with OS, including TTN (hazard ratio [HR]: 3.937, 95% confidence interval [CI]: 1.502-10.309, P = 0.005), PSA level at the diagnosis of cancer (HR: 4.337, 95% CI: 1.616-11.645, P = 0.004), duration of initial androgen deprivation therapy (HR: 2.982, 95% CI: 1.104-8.045, P = 0.031), neutrophil-to-lymphocyte ratio (HR: 3.963, 95% CI: 1.380-11.384, P = 0.011), and total PSA response (Class 1 [<0 response] compared to Class 2 [0-50% response], HR: 3.978, 95% CI: 1.278-12.387, P = 0.017). In conclusion, TTN of PSA remains an important prognostic marker in predicting therapeutic outcome in Chinese population who receive chemotherapy for mCRPC and have >50% PSA remission.
Keywords: castration-resistant prostate cancer; chemotherapy; docetaxel; prostate-specific antigen; survival; time to nadir.