Optimization of planning strategy of automated volumetric modulated arc therapy for esophageal cancer

  Background  In the process of radiotherapy planning for esophageal cancer, it is necessary to consider the dose constraints of multiple organs at risk. Automatic planning can effectively reduce the influence of human subjective factors on the quality of the plan.

  Objective  To comprehensively evaluate the optimization performance and clinical application value of double arc and single arc automatic volume modulated arc therapy (A-VMAT) for esophageal cancer based on auto planning technology, so as to realize the optimization of automatic plan design strategy.

  Methods  Sixteen patients with esophageal cancer who received treatment in our hospital from October 2018 to December 2020 were selected. Double arc manual VMAT (DA-M-VMAT) was designed manually by pinnacle³ planning system. The dose volume histogram parameters were collected as the optimization parameters of auto-planning to design the double arc A-VMAT (DA-A-VMAT) and single arc A-VMAT (SA-A-VMAT), respectively. The parameters of target areas and organs at risk of each plan were analyzed and compared statistically in order to evaluate the optimization performance of AP techniques in different radiation fields.

  Results  Target’s HI results of DA-M-VMAT plan and DA-A-VMAT plan were better than SA-A-VMAT plan, but only the pGTV had statistical difference (F=5.101; P=0.010). The average MUs of DA-A-VMAT plan was higher than that of DA-M-VMAT plan, while that of SA-A-VMAT plan was lower than that of DA-M-VMAT plan, without significant difference (F=1.317; P=0.278). For the total lung, the volume parameters of V₅, V₁₀ and other low-dose areas in A-VMAT plan were higher than those in DA-M-VMAT plan. The parameters of V₂₀ and above showed the opposite trend, and SA-A-VMAT had better lung tissue protection than DA-A-VMAT, but there was no significant difference (P > 0.05). For heart, the analysis results were consistent with those of the total lung for each dose volume parameter of V₂₀ and above.

  Conclusion  Compared with DA-M-VMAT, both DA-A-VMAT and SA-A-VMAT can achieve the best target dose distribution and lower normal tissue dose in patients with esophageal cancer. The SA-A-VMAT has a faster clinical delivery efficiency and is more suitable for clinical treatment.