Hypofractionated conformal HDR brachytherapy in hormone naïve men with localized prostate cancer : Is escalation to very high biologically equivalent dose beneficial in all prognostic risk groups?

Purpose: To analyze the long-term effect of local dose escalation using conformal hypofractionated high-dose-rate brachytherapy (HDR-BT) boost and pelvic external-beam radiation therapy (EBRT) in hormone-naive men with localized prostate cancer. Patients and Methods: A total of 579 men were consecutively treated with pelvic EBRT and dose escalating HDR-BT since 1986 in two prospective trials: 378 patients at William Beaumont Hospital (1991-2002), and 201 patients at Kiel University (1986-1999). BT optimization was done modulating both, the dwell times and spatial source positions. A short course of neoadjuvant/concurrent androgen deprivation therapy was given to 222 patients. Hormone-naive patients only (n = 324) with a follow-up > 18 months were analyzed. All patients had at least one poor prognostic factor (stage ≥ T2b, Gleason Score > 7, pretreatment prostate-specific antigen [PSA] > 10 ng/ml): any one factor 122 patients, any two factors 122 patients, and three factors 80 patients. This cohort was stratified by equivalent dose (ED): dose level 1, 94 Gy, n = 266, assuming an α/β ratio of 1.2. The ASTRO definition for biochemical failure was used. Results: Mean follow-up was 5.3 years (1.5-13.9 years). For all 324 patients, the 5-year biochemical control (BC) rate was 79%. Cancer-specific survival was 98%, and overall survival 90%. Similar analysis by institution demonstrated no difference in outcomes. For the entire cohort of hormone-naive men, dose escalation to > 94 Gy resulted in a better 5-year BC of 59% versus 85% (p 94 Gy. Conclusion: The results demonstrate that conformal HDR-BT is a successful method for delivering very high radiation dose to the prostate. The ability to escalate dose to ED > 94 Gy was reflected in improved long-term outcomes in terms of BC, significantly for those patients with two or three poor prognostic factors reaching BC rates of 85%.