Dose escalation with external beam radiation therapy and high-dose-rate brachytherapy combined with long-term androgen deprivation therapy in high and very high risk prostate cancer: Comparison of two consecutive high-dose-rate schemes

Abstract Purpose To compare rectal toxicity, urinary toxicity, and nadir+2 PSA relapse-free survival (bRFS) in two consecutive Phase II protocols of high-dose-rate (HDR) brachytherapy used at the authors institution from 2001 to 2012. Methods and Materials Patients with National Comprehensive Cancer Network high risk and very high risk prostate cancer enrolled in studies HDR4 (2001–2007, n = 183) and HDR2 (2007–2012, n = 56) were analyzed. Patients received minipelvis external beam radiation therapy/intensity-modulated external radiotherapy to 54 Gy and 2 years of androgen blockade along with HDR brachytherapy. HDR4 protocol consisted of four 4.75 Gy fractions delivered in 48 hours; the HDR2 protocol delivered two 9.5 Gy fractions in 24 hours. Average 2-Gy equivalent dose (α/β = 1.2) prostate D90 doses for the HDR4 and HDR2 groups were 89.8 Gy and 110.5 Gy, respectively ( p = 0.0001). Both groups were well balanced regarding risk factors. Prior transurethral resection of the prostate was more frequent in the HDR2 group ( p = 0.001). Results After a median followup of 7.4 years (range, 2–11.2), there was no difference in adverse grade ≥ 2 rectal events (HDR4 = 10.4% vs. HDR2 = 12.5%; p = ns) or grade ≥3 (HDR4 = 2.2% vs. HDR2 = 3.6%; p = ns). No differences in urinary grade ≥2 adverse events (HDR4 = 23% vs. HDR2 = 26.8%; p = ns) or grade ≥3 (HDR4 = 7.7% vs. HDR2 = 8.9%; p = ns) were detected. The 7-year bRFS for HDR4 and HDR2 protocols was 88.7% and 87.8%, respectively ( p = ns). Conclusions HDR4 and HDR2 protocols produce similar results in terms of toxicity and bRFS at the intermediate time point of 7 years.