Assessing the Role of Volumetric Modulated Arc Therapy (VMAT) Relative to IMRT and Helical Tomotherapy in the Management of Localized, Locally Advanced, and Post-Operative Prostate Cancer

Purpose To quantify differences in treatment delivery efficiency and dosimetry between step-and-shoot intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy (HT) for prostate treatment. Methods and Materials Twenty-five prostate cancer patients were selected retrospectively for this planning study. Treatment plans were generated for: prostate alone ( n = 5), prostate + seminal vesicles ( n = 5), prostate + seminal vesicles + pelvic lymph nodes ( n = 5), prostate bed ( n = 5), and prostate bed + pelvic lymph nodes ( n = 5). Target coverage, dose homogeneity, integral dose, monitor units (MU), and sparing of organs at risk (OAR) were compared across techniques. Time required to deliver each plan was measured. Results The dosimetric quality of IMRT, VMAT, and HT plans were comparable for target coverage (planning target volume V95%, clinical target volume V100% all >98.7%) and sparing of organs at risk (OAR) for all treatment groups. Although HT resulted in a slightly higher integral dose and mean doses to the OAR, it yielded a lower maximum dose to all OAR examined. VMAT resulted in reductions in treatment times over IMRT (mean = 75%) and HT (mean = 70%). VMAT required 15–38% fewer monitor units than IMRT over all treatment volumes, with the reduction per fraction ranging from 100–423 MU from the smallest to largest volumes. Conclusions VMAT improves efficiency of delivery for equivalent dosimetric quality as IMRT and HT across various prostate cancer treatment volumes in the intact and postoperative settings.