Dosimetric Comparison Of Intensity Modulated Tangential Beam Versus Conventional Tangential Irradiation For Breast Cancer

Objective:Breast-conserving therapy has become a widely accepted treatment option in the management of early-stagebreast cancer.Postoperative radiotherapy is conventionally delivered with conventional wedged tangential fields.However,intensity modulation in radiotherapy helps to maximize tumor control while minimizing damage to normal tissues。This study was to evaluate the potential dosimetricb benefits and optimal indications of intensity modulated radiotherapy(MRT)for the intact breast. Methods:Twenty patients with stage Tis-2N0M0breast cancer,who received breast-conserving surgery,were selected for this study.A dosimetric comparison foof forward planning MRT with conventional wedged tangential techique was performed on each patient using three-dimensional treatment planning.The total prescribed dose for both plans was 5000cGy/25 fractions.Dose volume histograms(DVH)were used to comparethe planning target volumn(PTV)and organs at risks(OARs)such as pisilateral lung,contralateral breast,contralateral lung for all patients.Results:The PTV coverage in MRT plan was similar to that of the conventional plan(99%vs.98%).A better dose uniformity throughout the whole breast was achieved by MRT plan.The percentage of PTV receiving less than 95%prescribed dose;The percentage of PTV receiving more than 105%prescribed dose(V105%)decreased form 3.6%to 0.31%.Received 30Gy by the heart(V30)was 4.6%±4.3%and 12.7%±6.3%(p＜0.001);V40 was 1.5%±2.1%and 8.3%±4.1%(p＜0.001)with IMRT and CR.Conclusion:Forward planning MRT based on a standard tangential beam arrangement significantly improves the dose homogeneity throughout the target volume of intact breast and reduces the dose to OARs.