Evaluation of Auto-Planning in VMAT for Locally Advaced Nasopharyngeal Carcinoma

The aim of this study is to demonstrate the feasibility of Auto-Planning module for locally advanced nasopharyngeal carcinoma (NPC). A total of 22 patients with locally advanced NPC were enrolled in this study. For each patient, volumetric modulated arc therapy (VMAT) plans were generated manually by an experienced physicist and automatically by the Auto-Planning module. The dose distribution, dosimetric parameters, monitor units and planning time were compared between automatic plans (APs) and manual plans (MPs). Meanwhile, the overall stage of disease was factored into the evaluation. The targets dose coverage of APs was similar to that of MPs. For most of the organs at risk (OARs) except spial cord, the dose parameters of APs were superior to that of MPs. The D max and V 50 of brain-stem were statistically decreased by 1.0 Gy and 1.32% respectively, while the D max of optic nerves and optic chiasm were also lower in the APs (both P < 0.05). APs provide a similar or superior plan quality to MPs in most cases, except for several patients with stage IV. The dose differences for most OARs were similar between the two types of plans and independent of the overall stage. Nevertheless, the APs provided better brain-stem sparing in patients with stage III, while better the parotid glands sparing in patients with stage IV. Moreover, the monitor units and planning time were significantly decreased in the APs. In general, Auto-Planning was a potential technology on the implementation of VMAT treatment planning for locally advanced NPC.