An investigation of the effect of using a hybrid technique on the quality of plans in breast cancer radiotherapy

In this study, it is aimed to make the dose applied to the tumor more homogeneous using hybrid planning techniques in breast cancer radiotherapy, and to increase local control by minimizing the dose applied to surrounding healthy tissues. Our thesis study was conducted retrospectively using CT images of 20 patients, 10 of whom were right and 10 of whom were left, diagnosed with breast cancer who had received radioretapy treatment. 3DCRT+IMRT, 3DCRT+VMAT and IMRT+VMAT hybrid plans obtained by 50% -50% weighted combinations of 3DCRT, IMRT, VMAT plans and IMRT + VMAT hybrid plans were prepared for each patient. Dose Volume Histogram (DVH) information was used to evaluate the quality of the treatment plan. The comparison parameters were determined as the Planned Target Volume (PTV), Critical Organ (OAR) dose values, Homogeneity Index (HI), Conformity Index (CI) values and Monitor Unit (MU) values. In our study, the best CI value for right and left breast irradiation was obtained in VMAT, and the HI value was obtained in IMRT+VMAT hybrid plans. The lowest values of V20(%) for the lung were obtained in the IMRT+VMAT hybrid plans, while the values of V5(%) and V10(%) were obtained in the 3DCRT, 3DCRT+IMRT and 3DCRT+VMAT hybrid plans. Contra breast doses have the lowest value in 3DCRT+IMRT, 3DCRT+VMAT hybrid plans. The left breast heart V30(%) value was the lowest technical VMAT, while the V5(%) volume was the lowest with 3DCRT, 3DCRT+IMRT, 3DCRT+VMAT hybrid plans. As a result of the study, it was seen that IMRT+VMAT, 3DCRT+IMRT, 3DCRT+VMAT hybrid plans increased the quality of the plan by reducing the same and contralateral lung dose, irradiated lung volume, contra breast dose, irradiated contra breast volume and heart dose during right and left breast irradiation. Keywords: Breast Cancer, Radiotherapy, Hybrid Planning, Treatment Plan Comparison