Dosimetric Investigation of FIF, VMAT, IMRT, H-VMAT, and H-IMRT Planning Techniques in Breast Cancer Radiotherapy.

OBJECTIVE It is aimed to compare the hybrid radiotherapy (RT) plans according to three-dimensional field-in-field (FIF), intensity-modulated RT (IMRT), and volumetric-modulated arc therapy (VMAT) techniques in RT applied to the whole breast volume after breast-conserving surgery. METHODS Based on the simulation images of 31 consecutive patients who received whole breast RT, a dose of 50 Gy (25 fractions) was prescribed to the planned treatment volume (PTV) with 6 MV X-rays, five new plans were created, respectively (FIF, VMAT, IMRT, H-VMAT, and H-IMRT). Homogeneity criteria for PTV, volume-dose criteria for peripheral critical organs, and MU values of the plans were evaluated separately for each plan. Subgroup analyses were performed for the left- and right-sided patients. RESULTS Both hybrid plans produced a more homogeneous plan at the target volume compared to the other three techniques (HI; 0.14, 0.14, 0.16, 0.12, and 0.13, p<0.001, respectively). Again, smaller values for D2% were obtained with both hybrid techniques (53.25, 53.24, 53.8, 52.41, and 52.47 Gy, respectively, p<0.001). The mean heart dose for the left-sided irradiations was 3.54, 3.40, 4.33, 3.49, and 3.79 Gy for the five techniques, respectively (p=0.029). Compared with FIF with the other four techniques for the left-sided irradiations, the LAD D 10% value was significantly reduced (p<0.001). CONCLUSION Hybrid plans provide a more homogeneous dose distribution compared to the use of other techniques alone, while at the same time, it allows reducing the ipsilateral lung and heart doses. [ABSTRACT FROM AUTHOR]