ABSTRACT
Background and purpose:Intensity-modulated radiotherapy(IMRT) can significantly improve the dosimetric distribution of both the target and organs at risk compared to tangential irradiation for whole breast. However,its optimized methods remain different and conflicting for many radiotherapy institutions.In order to achieve the optimized planning of IMRT for the irradiation of intact breast,we investigated different optimizing methods in three dimensional radiotherapy planning system.Methods:Ten patients with early-stage breast cancer after breast conserving surgery were eligible for the study.Two kinds of plans were performed on each patient in three-dimensional treatment planning system,inverse planning IMRT and forward planning IMRT which included 3 different optimizing methods as manual optimizing(MO),multiple points optimizing(PO) and automated inverse optimizing(AO).Various parameters were used to evaluate the efficacy of different IMRT plans.All plans were compared using dose volume histograms(DVH) for the planning target volume(PTV) and organs at risk(OARs).Results:For MO,PO,AO forward plans and inverse plans,median number of segments were 5,5.5,5 and 20 respectively,and mean total MU were 225.8, 228.4,226.4 and 345.8 MU,respectively.Comparing the different forward planning optimizations,the best target coverage and dose homogeneity of PTV was observed in AO plans(P(?)0.01),and PO and AO plans showed a better reduction of OARs exposure compared with MO plans(P(?)0.05).A further improvement of dose homogeneity in the PTV and better sparing of OARs was achieved using inverse planning(P(?)0.05).Conclusion:Forward planning IMRT with AO optimization for intact breast irradiation could provide both efficacy and dosimetric advantages better than others.The inverse IMRT plan showed more potential in improving the dosimetric outcomes.However,further studies are required for inverse optimizing plans.