(Saturday, 4/7/2018)
Room: Foyer
Purpose: To compare the dosimetric differences between Intensity modulated arc therapy (IMAT) and static intensity modulated radiotherapy (IMRT) for different PTV volume of esophageal cancer(ＥＣ).
Methods: Fourty patients who were diagnosed with thoracic EC. Including 10 cases located in the upper, middle and the lower thorax, respectively. IMAT and IMRT two plans were generated with the The Elekta Oncentra4.1 Planning System in Varian 23EX Linac, prescription dose of 60Gy in 30 fractions to the PTV. All treatment plans of the 40 cases were evaluated using the dose-volume histogram parameters of PTV and the organs at risk. The monitor units (MUs) were also examined.
Results: For PTV volume<50cm3 group (PTVs), IMAT plan had superior homogeneity when compared with IMRT plan, while the lung V5 and MLD were slightly higher for IMAT plan. For50 ~150cm3 group(PTVm), PTV D95 for VMAT got closer to prescription dose,IMAT plan resulted in a slightly lower lung V10 and higher lung V30. However, IMAT plan had lower V100 in the PTV, compared to IMRT plan for PTV volume >150cm3 group (PTVb), and sparing of lungs showed no statistically significant differences between the two techniques. When compared with IMRT plan, IMAT plan reduced the monitor units by an average of 15% and 25% in the PTVm group and PTVb group. However, IMAT plan provided an average of 13.5% more monitor units than IMRT plan in the PTVs group.
Conclusion: For PTVs IMAT is better than IMRT, not only in the treatment time but also in the PTV dose，is the first choice.In addition. IMAT plan provides equivalent conformal dose coverage and sparing of OARs for the PTVm EC with less delivery time. However, IMRT is the first choice for a PTVb EC, since IMAT plan with worse target volume coverage and even increases the spring of OARs.
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