BACKGROUND AND PURPOSE: To report long-term cancer control rates following high dose-rate (HDR) brachytherapy boost for intermediate risk prostate cancer and explore early biochemical predictors of success.
MATERIAL AND METHODS: Results of two sequential phase II trials are updated and compared: (1) Single 15Gy HDR-boost followed by external beam radiotherapy (EBRT) 37.5Gy/15fractions, (2) Two HDR fractions of 10Gy followed by EBRT 45Gy/25fractions. Patients were followed prospectively for clinical and biochemical outcomes. Nadir PSA (nPSA) and PSA at 3-years were analyzed as continuous variables, and ROC analysis was used to identify the optimal cutoff values. Kaplan-Meier bDFS curves were generated and the log-rank test used to compare different groups.
RESULTS: 183 patients were accrued; 123 to the single fraction trial and 60 to the standard fractionation trial, with a median follow-up of 74months and 99months, respectively. The 5-year biochemical relapse-free survival was 97.4% and 92.7%, respectively (p=0.995). Median nPSA was 0.08ng/ml. Failure to achieve a nPSA < 0.4ng/ml was associated with a significantly higher rate of biochemical relapse (5-year bDFS: 100% vs. 72%; p< 0.0001).
CONCLUSION: HDR boost with single fraction 15Gy provides durable long-term biochemical disease-free survival. PSA nadir < 0.4ng/ml is associated with very low risk of biochemical failure.
Helou J, D'Alimonte L, Loblaw A, Chung H, Cheung P, Szumacher E, Danjoux C, Ravi A, Deabreu A, Zhang L, Morton G. Are you the author?
Sunnybrook Odette Cancer Centre, Canada; University of Toronto, Canada.
Reference: Radiother Oncol. 2015 Mar 11. pii: S0167-8140(15)00117-6.