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

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 H-H 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), D_mean 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, D_mean, and D_50% 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, D_mean, and D_50%, 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, D_mean, and D_50% 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. (authors)