Evaluation of volumetric modulated arc therapy planning for rectal cancer based on Auto-Planning

Abstract

Objective To determine whether Auto-Planning-based volumetric modulated radiotherapy (Auto-VMAT) planning can improve planning efficiency without compromising plan quality compared with current manual trial-and-error-based volumetric modulated arc therapy (Manual-VMAT) planning for patients with rectal cancer. Methods Ten patients with stage Ⅱ-Ⅲ rectal cancer who underwent Dixon surgery were enrolled as subjects. The Pinnacle 9.10 planning system was used to design Manual-VMAT and Auto-VMAT plans. Dose distribution, homogeneity index (HI), conformity index (CI), Dmean values of different organs at risk or dose-volume histogram of regions of interest, total planning time, and manual planning time were compared between the two plans. The differences were analyzed by paired t test. Results Dosimetric prescriptions were achieved in both plans. There were no significant differences in HI or CI between the Auto-VMAT plans and the Manual-VMAT plans (0.058 vs. 0.058, P=0.972; 0.921 vs. 0.940, P=0.115). Compared with the Manual-VMAT plans, the V40, Dmean, and D50% of the bladder were significantly reduced by 25.6%, 11.5%, and 8.9%, respectively, in the Auto-VMAT plans (P=0.004, 0.016, 0.001); the V40, Dmean, and D50% of the small intestine were also significantly reduced by 12.1%, 5.4%, and 6.8%, respectively, in the Auto-VMAT plans (P=0.023, 0.001, 0.001); the V30, Dmean, and D50% of the left and right femoral heads were slightly reduced in the Auto-VMAT plans. The Auto-VMAT plans had significantly longer total planning time but significantly shorter manual planning time than the Manual-VMAT plans (50.38 vs. 36.81 min, P=0.000; 4.47 vs. 16.94 min, P=0.000). Conclusions Compared with the Manual-VMAT plans, the Auto-VMAT plans have substantially shorter manual planning time and improved planning efficiency. Key words: Rectal neoplasms/volumetric modulated arc therapy; Auto-planning; Plan evaluation