Selection of patients who would not require long-term prostate-specific antigen monitoring after low-dose-rate brachytherapy

Purpose: To identify patients at extremely low risk of biochemical recurrence (BCR) of prostate cancer after low-dose-rate brachytherapy (LDR-BT) to determine when prostate-specific antigen (PSA) monitoring can be stopped. Methods and Materials: We retrospectively reviewed clinicopathologic data of patients with prostate cancer who underwent LDR-BT between 2003 and 2011. Of 1569 patients reviewed, 689 (43.9%) received combination external beam radiotherapy, and 970 (61.8%) had neoadjuvant hormonal therapy. We stratified patients according to risk factors identified by multivariate analysis and assessed the factors for an association with BCR (defined as ≥2 ng/mL higher than the nadir). Results: The median followup was 96 months. Of 1531 patients who were BCR-free at 3 years after treatment, 76 subsequently developed BCR; of 1500 who were BCR-free at 5 years, 45 eventually had BCR. On multivariate analysis, independent risk factors for BCR were the National Comprehensive Cancer Network risk group at diagnosis and PSA levels at 3 or 5 years after radiotherapy. In the low-risk group, no patient with a PSA level ≤0.2 ng/mL at 3 years after radiotherapy subsequently developed BCR. In the intermediate-risk group, no patients with a PSA level ≤0.2 ng/mL at 5 years subsequently developed BCR. Conclusions: The National Comprehensive Cancer Network risk group at diagnosis and PSA values at 3 and 5 years after LDR-BT are independently associated with a risk of later BCR. Using these two factors may help to select patients for whom PSA monitoring could be stopped because they have an extremely low risk of later BCR.