Novel prognostic indexes clinically applicable for patients with Stage IV prostate cancer are needed because prostate-specific antigen (PSA) tests occasionally fail to reflect the prognostic outcome. We investigated various clinicopathologic parameters in men with Stage IV prostate cancer and evaluated the utility of the PSA/prostatic acid phosphatase (PAP) ratio as a prognostic index.

We reviewed 241 patients with Stage IV prostate cancer, who were treated in Niigata Cancer Center Hospital from 1992 to 2004. Survival curves were generated using the Kaplan-Meier method. Univariate and multivariate analyses of survival associations, including age, performance status, clinical presentation, disease localization, pathologic findings, and serologic markers, were conducted using the log-rank test and Cox proportional hazard models.

The 5-year overall survival rate using the Kaplan-Meier method for all 241 patients was 43.0%. No significant difference was found in the survival rates according to PSA level. However, the 5-year survival rate was significantly lower in patients with a PSA/PAP ratio of less than 3.0 (P = 0.0022): 24.2% and 48.0% in those with a PSA/PAP ratio of less than 3.0 and 3.0 or greater, respectively. On multivariate analysis using the proportional hazards model, the statistically significant prognostic factors of overall survival were alkaline phosphatase (P = 0.0413), lactate dehydrogenase (P = 0.0409), and the PSA/PAP ratio (P = 0.0113).

The PSA/PAP ratio is a valuable prognostic indicator in men with Stage IV prostate cancer. Although our study found that other laboratory tests also had a prognostic influence, the PSA/PAP ratio was an essential index implicated in the physiopathology of prostate cancer.