Long-Term Prostate Specific Antigen Stability and Predictive Factors of Failure after Permanent Seed Prostate Brachytherapy

Purpose: Defining biochemical failure as nadir + 2 may overestimate cure after radiotherapy. We assessed long-term prostate specific antigen stability after low dose rate prostate brachytherapy and predictors of biochemical failure when prostate specific antigen was slowly rising below the nadir + 2 ng/ml threshold.Materials and Methods: A total of 2,339 patients with low or intermediate risk prostate cancer received 125iodine brachytherapy from 1998 to 2010 with a minimum 3-year followup. In addition, 49.7% of the patients received 6 months of androgen deprivation. Clinical, dosimetric and prostate specific antigen data were retrieved from a prospective database. Biochemical results were classified as stable or rising prostate specific antigen (0.2 ng/ml or greater and increased 0.1 ng/ml or greater during the preceding 2 years), or biochemical failure (defined as nadir + 2). Multivariate analysis was done to identify predictors of failure used to create logistic regression models.Results: At a median fo...