核医学と放射線治療

A Dosimetric Comparison of Volumetric Modulated Arc Therapy (VMAT) with Unflattened Beams to VMAT with Flattened Beams and Tomotherapy for Head and Neck Cancer

Abstract

Toshiyuki Ogata, Hideki Nishimura, Hiroshi Mayahara, Aya Harada, Yoshiro Matsuo, Masao Nakayama, Kazuyuki Uehara, Shinji Tsudou, Yasuo Ejima, Ryohei Sasaki and Takanobu Okayama

Background: The purpose of this study was to compare the dose distributions and treatment delivery efficiency of volumetric modulated arc therapy (VMAT) with flattening filter free (FFF) beams (FFF-VMAT) against VMAT with flattening filter (FF) beams (FF-VMAT) and Helical TomoTherapy (HT) for head and neck cancer.

Methods: Ten patients with nasopharyngeal and oropharyngeal cancer were chosen for this planning comparison study. Three treatment plans (dual arc FFF-VMAT, dual arc FF-VMAT, and HT) were created for each patient. The three prescription dose levels of the planning target volumes were 69.96, 60, and 54 Gy in 33 fractions, using the simultaneous integrated boost technique. Comparisons of the plan quality were performed by analyzing the homogeneity, conformity, dose to the organs at risk (OARs), the number of monitor units (MUs), and beam-on time (BOT) necessary for delivering the plans.

Results: The target coverage and sparing of the OARs for FFF-VMAT were almost equivalent to those for FFVMAT and HT. Compared to FF-VMAT, FFF-VMAT and HT significantly increased the number of MUs. The BOTs were the same for FFF-VMAT and FF-VMAT but significantly increased for HT.

Conclusion: We here present the first report of FFF-VMAT achieving a comparable plan quality with less delivery time to that of FF-VMAT and HT in head and neck cancer. FFF-VMAT is a highly efficient and feasible option for the treatment of head and neck cancer in clinical practice.