Volumetric Modulated Arc Therapy (VMAT) in the Treatment of Localized Prostate Cancer: Initial Experience in 200 Patients

Abstract

Purpose/Objective(s): To report initial experience of biochemical outcomes and the acute and late toxicity in 200 patients with clinically localized prostate cancer treated with volumetric modulated arc therapy (VMAT). Materials/Methods: Between November 2007 and September 2011, 200 patients with clinically localized prostate cancer were treated with VMAT using daily cone-beam computed tomography acqusition. Treatment planning systems used were avoidance conformal-based in 77 patients and multileaf collimator-based in 123 patients. All plans were generated on an inverse-planning approach. A total of 182 patients (91%) were treated to 76 Gy, and 18 patients (9%) were treated to Z < 72 Gy. Acute and late toxicities were scored according to CTCAE grading scales. PSA relapse was defined according to Phoenix definition. The mean follow-up time was 50 months (range: 7-85 months). Results: Two patients (1%) developed acute Grade 2 or worse GI toxicity. Thirty-nine patients (19%) developed acute Grade 2 GU symptoms, and no one experienced Grade 3 GU toxicity. Six patients (3%) developed late Grade 2 rectal bleeding. Two patients (1%) experienced Grade 3 rectal toxicity requiring either one or more transfusions or a laser cauterization procedure. No Grade 4 rectal complications have been observed. The 5year actuarial likelihood of late Grade 2 or higher rectal bleeding was 3.4%. Twenty patients (10%) experienced late Grade 2 GU toxicity, and no one developed Grade 3 GU toxicity. The 5-year actuarial likelihood of late Grade 2 or higher GU toxicity was 11.6%. The 5-year actuarial PSA relapse-free survival rates for low-, intermediate-, and high-risk group patients stratified according to NCCN criteria, were 100%, 91,8%, and 85.3%, respectively. Conclusions: Our initial data demonstrate the feasibility of VMAT in patients with localized prostate cancer. Acute and late rectal toxicities seem to be dramatically reduced compared with what has been observed with conventional radiation therapy techniques. Short-term PSA control rates were excellent. Based on our promising initial experiences, VMAT is an established novel conformal radiation delivery method for localized prostate cancer at our institution. Further studies in a larger population are required to determine long-term results in VMAT. Author Disclosure: K. Shiraishi: None. K. Yamamoto: None. A. Haga: None. A. Sakumi: None. K. Nakagawa: None.