Long-term outcomes of whole-pelvis radiation therapy using volumetric modulated arc therapy for high-risk prostate cancer

Abstract

This study investigated the outcomes of whole-pelvis radiation therapy (WPRT) using volumetric modulated arc therapy (VMAT) for high-risk prostate cancer. We retrospectively analysed 112 patients with high-risk prostate cancer who started WPRT at our hospital between August 2011 and August 2015. The prescribed dose was 78 Gy in 39 fractions to the prostate and 46.8 Gy in 26 fractions to the pelvic lymph node (LN) area. All patients received long-term androgen deprivation therapy. We evaluated late gastrointestinal (GI) and genitourinary (GU) toxicities using the Common Terminology Criteria for Adverse Events version 4.0. The median follow-up period for censored cases was 97 (interquartile range [IQR] = 85–108) months. The median age was 72 (IQR = 67–75) years. The high-risk and very-high-risk groups included 41 (36.6%) and 71 patients (63.4%), respectively. The median risk of LN invasion calculated by the Roach formula was 36.9 (IQR = 26.6–56.3) %. The 8-year overall survival, biochemical failure-free survival, disease-free survival and distant metastasis-free survival rates were 88.4, 91.9, 83.8 and 98.0%, respectively. Only one patient experienced common iliac LN recurrence, which was outside the pelvic irradiation area. All patients with recurrent disease were categorized into the very-high-risk group. The 8-year cumulative rates of ≥Grade 2 late GI and GU toxicities were 12.8 and 11.8%, respectively. No patients experienced Grade 4 or higher toxicities. WPRT using VMAT for high-risk prostate cancer was well tolerated and effective.