Prostate-specific antigen half-life and pretreatment prostate-specific antigen: Crucial predictors for prostate-specific antigen trend in delayed-combined androgen blockade therapy

Purpose: To elucidate the crucial predictors for prostate-specific antigen (PSA) trends and determine the usage of anti-androgen treatment during delayed-combined androgen blockade (CAB) leading to a PSA level below 0.2 ng/mL. Materials and Methods: From January 2001 to December 2004, 105 prostate cancer patients were enrolled. Medical castration and anti-androgen treatment were used sequentially and termed delayed-CAB. The first goal was to maintain an undetectable PSA level. The nadir PSA was determined after medical castration only. Anti-androgen was given if a PSA level of more than 0.2 ng/mL was observed and the subsequent PSA response was assessed. All cases were divided into two groups based on whether the PSA was lower (n = 59) or higher (n = 46) than 0.2 ng/mL. An analysis of the difference between the two groups was calculated. Results: The median of the initial PSA level in the lower group was lower than in the higher group with a 95% cut-off level of 40 ng/mL. The median PSA half-life in the lower group was also reduced with a 95% cut-off of 3.6 months. In a multivariate analysis, the pretreatment PSA level and the PSA half-life exhibited a significant correlation between the two groups. Anti-androgen treatment was given to 26 cases in the higher group. The PSA increased in one case, decreased to less than 0.2 ng/mL in 17 cases and remained over 0.2 ng/mL in eight cases. Conclusion: Both the PSA half-life and the pretreatment PSA level were useful markers for predicting the PSA trends to determine the optimal use of anti-androgen treatment during delayed-CAB.