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

Objectives

To evaluate prognostic factors of biochemical recurrence (BCR) in each risk group of prostate cancer patients who underwent low-dose-rate brachytherapy (LDR-BT).

Methods

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.

Results

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.

Conclusions

LDR-BT can achieve a higher recurrence-free survival with an adequate local radiation dose (BED ? 180 Gy2).