Prostate-specific antigen halving time while on neoadjuvant androgen deprivation therapy is associated with biochemical control in men treated with radiation therapy for localized prostate cancer.

Abstract

To assess whether the PSA response to neoadjuvant androgen deprivation therapy (ADT) is associated with biochemical control in men treated with radiation therapy (RT) for prostate cancer. In a cohort of men treated with curative-intent RT for localized prostate cancer between 1988 and 2005, 117 men had PSA values after the first and second months of neoadjuvant ADT. Most men had intermediate-risk (45%) or high-risk (44%) disease. PSA halving time (PSAHT) was calculated by first order kinetics. Median RT dose was 76 Gy and median total duration of ADT was 4 months. Freedom from biochemical failure (FFBF, nadir + 2 definition) was analyzed by PSAHT and absolute PSA nadir before the start of RT. Median follow-up was 45 months. Four-year FFBF was 89%. Median PSAHT was 2 weeks. A faster PSA decline (PSAHT ≤2 weeks) was associated with greater FFBF (96% vs. 81% for a PSAHT >2 weeks, p = 0.0110). Those within the fastest quartile of PSAHTs (≤ 10 days) achieved a FFBF of 100%. Among high-risk patients, a PSAHT ≤2 weeks achieved a 4-yr FFBF of 93% vs. 70% for those with PSAHT >2 weeks (p = 0.0508). Absolute PSA nadir was not associated with FFBF. On multivariable analysis, PSAHT (p = 0.0093) and Gleason score (p = 0.0320) were associated with FFBF, whereas T-stage (p = 0.7363) and initial PSA level (p = 0.9614) were not. For men treated with combined ADT and RT, PSA response to the first month of ADT may be a useful criterion for prognosis and treatment modification.