Population-based Study of Biochemical and Survival Outcomes After Permanent 125I Brachytherapy for Low- and Intermediate-risk Prostate Cancer

Abstract

To analyze the biochemical and survival outcomes after permanent low-dose-rate prostate brachytherapy in a large, consecutive, population-based cohort of patients. A total of 1006 consecutive implants were performed from July 20, 1998 to October 23, 2003 for men with low-risk and "low-tier" intermediate-risk prostate cancer. The prescribed minimal peripheral dose was 144 Gy, using 0.33 mCi (125)I sources and a preplan technique with a strong posterior-peripheral dose bias. Most patients (65%) had received 6 months of androgen deprivation therapy. Supplemental external beam radiotherapy was not used. The prognostic features, dose metrics, and follow-up data were prospectively collected. Kaplan-Meier and Cox regression analyses were used to assess the factors associated with freedom from biochemical recurrence and survival. The median patient age at treatment was 66 years. The median follow-up was 54 months for biochemical outcomes and 66 months for survival. The actuarial freedom from biochemical recurrence rate was 95.6% +/- 1.6% at 5 years and 94.0% +/- 2.2% at 7 years. On multivariate analysis, the pretreatment prostate-specific antigen level (P = .03) and androgen deprivation therapy use (P = .04) were predictive of the freedom from biochemical recurrence. The actuarial rates of distant metastasis and disease-specific death at 5 years were both <1%. The overall survival rate at 5 years was 95.2% +/- 1.4% and was 93.4% +/- 1.8% at 7 years. On multivariate analysis, only age was predictive of overall survival (P = .011). When consistently planned and delivered, low-dose-rate brachytherapy, without supplemental external beam radiotherapy or intraoperative planning, can produce cancer-specific outcomes for men with low- and "low-tier" intermediate-risk prostate cancer at least equal to that produced by dose-escalated external beam radiotherapy or surgical prostatectomy.