Locoregional irradiation including internal mammary nodal region for left-sided breast cancer after breast conserving surgery: Dosimetric evaluation of 4 techniques

Abstract The present study aimed to compare 4 techniques in the planning of locoregional irradiation including internal mammary nodal region for left-sided breast cancer. Ten patients with left-sided breast cancer undergoing breast conservation surgery were enrolled. For each patient, 4 treatment plans were performed: a helical tomotherapy (HT) plan, a volumetric modulated arc therapy (VMAT) plan, a static intensity modulated radiation therapy (IMRT) plan, and a hybrid IMRT plan, designed to encompass the whole breast, internal mammary, and supraclavicular nodal regions. The prescribed dose of radiation was 50 Gy in 25 fractions. The dosimetric parameters of the target and organs at risk, as well as the dose delivery time, were evaluated and compared using an independent-samples t-test. The HT and VMAT plans had the best conformity and homogeneity. For the HT, VMAT, IMRT, and hybrid IMRT plans, the mean conformity index (CI) and homogeneity index (HI) were 0.83, 0.82, 0.8, and 0.77 ( p p 55 values were 0.3%, 11.4%, 27.02%, and 23.29% ( p mean and V 20 of the left lung obtained using the HT plan were significantly lower than those of VMAT, IMRT, and hybrid IMRT plans ( p  = 0.002, p  = 0.004). There were no significant differences in D max of LAD descending coronary artery, or the D mean of the heart among the 4 types of plans. The HT and VMAT plans had a lower dose to other organ at risk (OARs) compared with the IMRT and hybrid IMRT plans. The mean delivery times were 1042 ± 33 seconds, 136 ± 12 seconds, 450 ± 65 seconds, and 451 ± 70 seconds for the HT, VMAT, IMRT, and hybrid IMRT plans, respectively ( p