Comparison of biologically effective dose for treatment planning in the fixed-beam intensity-modulated radiotherapy and the volumetric-modulated arc therapy for the typical types of cancer

Purpose: To compare the fixed-beam intensity-modulated radiotherapy (IMRT) with the volumetric-modulated arc therapy (VMAT) plans for different cancers using the biologically effective dose (BED). Methods: Recruited patients were divided into three groups in terms of tumor anatomic site, including head and neck, thoracic, and abdominal cancers. All of plans were generated using the fixed-beam IMRT and the VMAT techniques. The qualities of the plans were assessed using the conformity index (CI) and the homogeneous index (HI) with respect to the dose delivered to the tumors. Some selected organs-at-risk (OARs) were analyzed. For the efficiency of the plan, monitor units (MUs) were compared between the paired plans. All parameters were collected and evaluated based on the conventional dose-volume histogram (DVH) of the paired plans. All BED were calculated from the physical dose. Results: For CI and HI, the fixed-beam IMRT and the VMAT gained significant differences (p < 0.05), mainly in the head and neck (HN) group, with the exception of the CI of the plan gross tumor volume (PGTV) in the nasopharyngeal carcinoma (NPC) site. In the thoracic group, the HI gained significant differences (p < 0.05) in the plans of the lung cancer with the central tumor without lymph node metastasis. The CI gained significant differences (p < 0.05) in the plans of the lung cancer with the surrounding tumor without lymph node metastasis. The MUs were higher in the VMAT plans compared with the fixed-beam IMRT plans in only two types of cancers. Analysis of the statistical significances regarding the BED values between the fixed-beam IMRT and the VMAT plans were the same as the values of the physical doses when the two paired plans were analyzed. Conclusion: There is no difference in the data comparison of the paired plans using the BED values compared with the physical doses.