Long-term outcome of whole pelvis radiotherapy and stereotactic body radiotherapy boost for intermediate and high risk prostate cancer

Background: We report our long-term outcomes with Cyberknife to deliver hypofractionated SBRT boost combined with EBRT to patients with intermediate to high risk prostate cancer. Materials an‎d Methods: From March 2008 to July 2014, 42 patients with newly diagnosed, intermediate (73.8%, 31) and high risk (26.2%, 11) localized prostate cancer were treated with EBRT and SBRT boost. The whole pelvis dose was 45 Gy (25 fractions of 1.8 Gy) and the SBRT boost dose was 21 Gy (3 fractions of 7 Gy). Results: With a median follow-up duration of 84.2 months (range, 20-139.6), the median PSA decline rates were -0.605, -0.229, -0.166 and -0.094 ng/mL/month, respectively, for durations of 1, 2, 3 and 4 years after radiotherapy and has remained near plateau. Four BCFs were observed only in high risk group. The actuarial 8 year BCF free survival and overall survival were 90.3 % and 83.7 %, respectively. BCF-free survival at 8 years were 100 % and 77.8 % for intermediate and high risk group, respectively (p=0.014). No grade 3 or 4 acute and late genitourinary (GU) and gastrointestinal (GI) toxicities were observed. Acute grade 2 GU toxicities were seen in 23.8 % (n = 10) and acute grade 2 GI toxicities in 21.4 % (n = 9). Late grade 2 GU toxicities were observed in 11.9 % (n = 5) and grade 2 GI toxicities in 14.2 % (n = 6). Conclusions: We demonstrated that SBRT boost after EBRT in intermediate- and high-risk prostate cancer had favorable outcomes with tolerable toxicities.