Hegde JV, et al. - Researchers examined biochemical relapse-free survival (BRFS) in men with National Comprehensive Cancer Network-defined intermediate-risk prostate cancer (PC) treated with either stereotactic body radiotherapy (SBRT) or high-dose-rate brachytherapy (HDR-B) monotherapy. Excellent BRFS was seen in intermediate-risk PC with SBRT and HDR-B monotherapy over a median follow-up of 4 years. Findings suggested these hypofractionated approaches are promising relative to standard fractionation outcomes despite the necessity for longer-term follow-up to determine the ultimate efficacy of these approaches.

Methods

• Researchers performed a retrospective, multi-institutional analysis of 437 patients with intermediate-risk PC treated with SBRT (N=300) or HDR-B (N=137).
• Those who underwent SBRT were treated to 35 to 40 Gy in 4 to 5 fractions.
• A total of 95.6% were treated to 42 Gy in 6 fractions among those who underwent HDR-B.
• Comparison of baseline patient characteristics was performed using a T test for continuous variables and the Mantel-Haenszel X² metric or Fisher exact test for categorical variables.
• To estimate 5-year actuarial BRFS, researchers generated Kaplan-Meier curves.
• Factors associated with biochemical failure were assessed using multivariate analysis using a Cox proportional-hazards model.

Results

• The mean age of 68.4 (SD±7.8) years was noted at diagnosis, and T-category was T1 in 63.6% and T2 in 36.4%.
• Findings suggested mean initial prostate-specific antigen of 7.4 (SD±3.4) ng/mL.
• Biopsy Gleason score of ≤3+4 in 82.8% and 4+3 in 17.2% was noted.
• The BRFS rate (Phoenix definition) was 96.3% at a median of 4.1 years of follow-up; no difference was noted when stratifying by treatment modality or biologically equivalent dose (BED1.5).
• Age (hazard ratio 1.08, P=0.04) and biopsy Gleason score (hazard ratio 2.48, P=0.03) were noted to be significant predictors of BRFS in multivariate analysis.