Dosimetric and Efficiency Comparisons between Volumetric Modulated Arc Therapy and IMRT for Cervical-Thoracic Esophageal Cancers

Abstract

Purpose: This study aims to evaluate the treatment plans of Volumetric-mo dulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) techniques for cervical-thoracic esophageal cancers. Methods and Materials: Sixty patients were retrospectively identified. Several parameters were evaluated based on target conformity and dose-volume histograms of organs at risk (lung, spinal cord, and heart). A phantom for time comparison was also assessed for each plan. Results: The IMRT plans (5f-IMRT: V95% = 99.4 ± 0.3, 7f-IMRT: V95% = 99.8 ± 0.1) results in better PTV coverage than RA plans (Single-arc: V95% = 95.8 ± 3.2, Double-arc: V95% = 95.4 ± 2.3). The target dose conformity of the 5f-IMRT plan was inferior to all plans (CI = 70.4 ± 7.1). The Single-arc plan achieved the best conformity (CI = 72.5 ± 4.6), whereas the Double-arc plan (CI = 72.1 ± 5.1) was slightly inferior to the Single-arc plan but superior to the 7f-IMRT plan (CI = 71.7 ± 8.6). The total MU was reduced by 42.1% in VMAT plan. The average MU needed to deliver the dose of 60 Gy for Single-arc (423.5 ± 52.1 MU) was found to be the least. Similarly, the average MU for the 5f-IMRT, 7f-IMRT and Double-arc were 868.2 ± 182.0 MU, 870.0 ± 225.3 MU and 548.8 ± 47.2 MU, respectively. The delivery time in VMAT plans was reduced from 193.8 seconds to 99.2 second s by around 48.8% compared to IMRT plans. Co nclusion: For similar PTV parameters, VMAT delivers a lower dose t o organs at risk than IMRT in a shorter time, and this has warranted clinical implementation.