Prediction of PSA bounce after permanent prostate brachytherapy for localized prostate cancer

Background: We aimed to calculate the frequency and features of the development of a prostate-specific antigen (PSA) bounce after prostate brachytherapy alone, to correlate the bounce with clinical and dosimetric factors and to identify factors that predict PSA bounce. Methods: PSA bounce was evaluated in 86 patients with T1-T2 prostate cancer who underwent radioactive seed implantation using iodine-125 (I-125) without hormonal therapy or external-beam radiation therapy (EBRT) from September 2004 to December 2007. A PSA bounce was defined as a rise of at least 0.4 ng/ml greater than a previous PSA level with a subsequent decline equal to, or less than, the initial nadir. Results: Calculated by the Kaplan-Meier method, the incidence of PSA bounce at a 2-year follow-up was 26%. Median time to the PSA bounce was 15 months. Univariate analysis demonstrated that age, dose received by 90% of the prostate gland (D90), volume of gland receiving 100% of the prescribed dose (V100), and V150 were significantly associated with the PSA bounce, while pretreatment PSA level, Gleason score, pretreatment prostate volume, clinical T stage, and V200 were not. In multivariate analysis, age 67 years or less and D90 more than 180 Gy were identified as independent factors for predicting the PSA bounce (P < 0.05). Conclusion: PSA bounce is not a rare phenomenon after prostate brachytherapy. It is more common in younger patients and patients receiving higher doses of radiation.