Ten-year biochemical relapse-free survival after external beam radiation and brachytherapy for localized prostate cancer: the Seattle experience

Abstract

Purpose: The role of external beam radiation therapy in addition to brachytherapy continues to be scrutinized for long term control of PSA levels after prostate cancer diagnosis.

Methods and materials: We report 10-year biochemical relapse-free survival (BRFS) on 232 patients presenting with localized prostate cancer and consecutively treated with iodine(125) (I(125)) or palladium(103) (Pd(103)) brachytherapy and neoadjuvant external beam radiation therapy. Multivariate regression analysis was used to create a pretreatment clinical prognostic risk model using a modified ASTRO consensus definition (two consecutive rises in serum PSA) as the outcome. Gleason scoring was performed by pathologists at a small community hospital. Derived risk categories are the following: low = PSA <or=10 ng/mL, Gleason sum score <7, and stage <T2c; intermediate = PSA >10 ng/mL or Gleason Score >or=7 or stage >or=T2c (1 intermediate risk factor); and high = 2 or more intermediate risk factors. Time to PSA failure (local, distant, or biochemical) was calculated and compared using Kaplan-Meier plots.

Results: Ten-year BRFS for the entire treatment group was 70%. Biochemical control rates by risk cohort analysis (95% confidence interval): low risk, 85% (83.3-90.7%); intermediate risk, 77% (73.0-84.5%); and high risk, 45% (45.4-57.2%). Using a risk grouping proposed by the Mt. Sinai group, the BRFS was: low risk, 84%; intermediate risk, 93%; and high risk, 57%. Grouping by the risk classification used by D'Amico, the BRFS was: low risk, 86%; intermediate risk, 90%; and high risk, 48%.

Conclusions: I(125) or Pd(103) brachytherapy, as a boost combined with EBRT, continues to result in high rates of biochemical control at 10 years. Different risk group classification schemes lead to different BRFS results.