Field-in-field IMRT versus 3D-CRT of the breast. Cardiac vessels, ipsilateral lung, and contralateral breast absorbed doses in patients with left-sided lumpectomy: a dosimetric comparison.

PURPOSE: This study evaluated dose distribution and homogeneity of field-in-field intensity-modulated radiation treatment (FIF-IMRT) compared with standard wedged tangential-beam 3D conformal radiotherapy (CRT) of the left breast in patients who have undergone lumpectomy. Our aim was to improve dose-distribution homogeneity in the breast and decrease the dose to organs at risk (OAR), i.e, heart and vessels, ipsilateral lung, and contralateral breast.

MATERIALS AND METHODS: FIF-IMRT and wedge plans of 3D-CRT were carried out for 18 patients with cancer of the left breast. Plans were compared according to cumulative dose-volume histogram (c-DVH) analysis in terms of planned treatment volume (PTV), homogeneity index (HI), and conformity index (CI), as well as dose and volume parameters of OARs.

RESULTS: When the targeted volumes receiving 105 % and 110 % of the prescribed dose in the PTV were compared, significant decreases were found with the FIF-IMRT technique. With the 105 % dose to the OARs, monitor unit (MU) counts were significantly lower with the FIF-IMRT technique. V2 of pulmonary artery, left atrium, and aorta and V1 for the contralateral breast were statistically significantly lower with FIF-IMRT plans (p = 0.001). PTV showed a better HI and CI with FIF-IMRT.

CONCLUSIONS: FIF-IMRT enables better dose distribution in the PTV and reduces dose to OARs in breast cancer radiotherapy.