Time to castration resistance is a novel prognostic factor of cancer-specific survival in patients with nonmetastatic castration-resistant prostate cancer

We aimed to identify prognostic factors of cancer-specific survival (CSS) in non-metastatic castration-resistant prostate cancer (M0CRPC) patients. The final analysis of this retrospective cohort included 82 patients who were diagnosed as M0CRPC between 1998 and 2018 at the University of Tokyo Hospital. CRPC was defined as prostate-specific antigen (PSA) progression (increased PSA ≥ 25% and ≥ 2 ng/mL above the nadir or detection of a metastatic lesion). The median value of age and PSA at the time of CRPC were 76 (range 55-94) years and 2.84 (range 2.04-22.5) ng/mL, respectively. The median follow-up time from CRPC diagnosis was 38 (range 3-188) months. The prognostic factors of CSS were 'PSA doubling time (PSADT) ≤ 3 months', 'time to CRPC diagnosis from the start of androgen deprivation therapy (TTCRPC) ≤ 12 months', of which TTCRPC was a novel risk factor of CSS. In the multivariate analysis, 'PSADT ≤ 3 months' and TTCRPC ≤ 12 months' remained as statistically significant predictors of CSS. Novel risk stratification was developed based on the number of these risk factors. The high-risk group showed a hazard ratio of 4.416 (95% confidence interval 1.701-11.47, C-index = 0.727).