Room: ePoster Forums
Purpose: To improve VMAT plan quality of non-small cell lung cancer through the evaluation and comparation of the constrain parameters of the maximum delivery time.
Methods: Thirty non-small cell lung cancer cases who were treated between July and September of 2018 were retrospectively studied by different maximum delivery time settings, 90s, 120s, and 150s. All the VMAT plans were demanded to achieve 60 Gy in 30 fractions to 95% of PTV, the target coverage followed the institutional clinical protocol. Plans consisted of 1 to 2 coplanar arcs were created using Oncentra 4.3 version and were delivered on an Elekta Synergy linear accelerator. The ability of PTV to meet dose-volume constraints, the normal lung V5, V10, V20, V30, mean lung dose and other organs at risk doses were compared and evaluated.
Results: The VMAT treatment plan quality of non-small cell lung cancer cases optimized by 120s of the parameter of maximum delivery time were both significantly superior to 90s plans in the mean dose, D50, D2 and V105 of PTV and 150s plans in the mean dose, D2 and V105 of PTV. In terms of OARs, the 150s VMAT plans reduced V20, V25 and V30 of lung tissue dose significantly compared to 120s plans, however yielded a worse PTV dose coverage. 120s VMAT plans were capable to produce higher quality than 90s and 150s plans in cord D2, p=0.014 and 0.005 respectively. No statistical significance was found in the comparison of other indicators.
Conclusion: 120s of maximum delivery time was capable of producing higher quality treatment plans than other parameters for non-small cell lung cancer VMAT cases. However, 150s would be the proper optimization setting to reduce lung dose for some abnormal pulmonary functions cases.
Not Applicable / None Entered.