Local dose (biologically effective dose ≥180 Gy2) is an important predictor of biochemical recurrence in patients undergoing low-dose-rate brachytherapy.

Abstract

To evaluate prognostic factors of biochemical recurrence (BCR) in each risk group of prostate cancer patients who underwent low-dose-rate brachytherapy (LDR-BT). A total of 944 patients with clinically confirmed prostate cancer (cT1c-3aN0M0) who had underwent LDR-BT were enrolled. The low-, intermediate-, and high-risk groups included 278, 498, and 168 patients, respectively. The median age, PSA value at diagnosis, and the follow-up period were 70 years (range: 48-84), 7.2 ng/ml (range: 1.2-113), and 91 months (range: 2-192), respectively. We evaluated the BCR-free rate, BCR-free survival, clinical recurrence-free rate, overall survival (OS), and cancer-specific survival (CSS). We conducted multivariate analysis to elucidate prognostic factors of BCR for all patients and for each risk group. The 5- and 10-year OS rates were 96.0% and 89.5% and the 5- and 10-year CSS rates were 99.8% and 99.1%, respectively, while the 5- and 10-year BCR-free rates were 96.6% and 92.5% in low-risk patients, 95.7% and 90.7% in intermediate-risk patients and 93.8% and 89.0% in high-risk patients, respectively. There were no significant differences between the risk groups. Age-adjusted multivariate analysis indicated biologically effective dose (BED) <180 Gy2 as an independent prognostic factor of BCR in all patients (p = 0.005). There were no independent factors in the low- and high-risk groups, but neoadjuvant androgen deprivation therapy (ADT) (p = 0.022) and BED <180Gy2 (p = 0.042) were independent prognostic factors in the intermediate-risk group. LDR-BT can achieve a higher recurrence-free survival with an adequate local radiation dose (BED ≥ 180 Gy2).