Comparison of Lung and Contralateral Scattered Breast Dose between Field-in-Field and Wedge Techniques in Patients with Early Breast Cancer

Purpose: This study aims to evaluate the dosimetric result of the Field-In-Field (FIF) plans compared with Tangential Wedged Beams (TWB) plans for whole breast radiotherapy of patients. Materials and Methods: In this survey, we entered fifty patients with breast-conserving surgery and postoperative whole-breast radiotherapy. FIF and a TWB plan were made for each patient to compare dosimetric outcomes. Results: The Homogeneity Index (HI) and Conformity Index (CI) were specified for the evaluation of Planning Target Volume (PTV). The mean dose of the ipsilateral lung and contra-lateral breast for the evaluation of organs at risk dose were used. The FIF plans had significantly lower HI (p 0.01) and CI (p 0.01) than those of the TWB plans. It means in the dosimetric comparisons of the PTV, the FIF plans were better than the TWB plans. The V10lung (31.152vs. 32.72%, p 0.01), V20lung (25.6064vs. 26.6%, p 0.01) V30lung (17.4% vs. 18.4%, p 0.01) were lower with the FIF plans compared with those of the TWB plans, with statistical significance. The FIF plans had a lower mean dose for the lung than those of TWB plans (1225.48 vs. 1670.32 cGy) but no statistical significance (p=0.06). The mean dose in the contra-lateral of the breast in FIF plans was lower than in TWB plans (61.666 vs. 163.45 cGy), with statistical significance (p 0.01). Conclusion: The FIF plans increased the dose homogeneity, and conformity of the target volume for the whole-breast irradiation compared with the TWB plans contralateral breast. Moreover, the doses of organs at risk (ipsilateral lung and contralateral breast) were reduced with FIF plans.