Dosimetric comparison of whole breast radiotherapy using field in field and conformal radiotherapy techniques in early stage breast cancer

We aimed to compare field-in-field technique (FIF) with conformal tangential field radiotherapy (CRT) in terms of dosimetric benefits for early stage breast cancer radiotherapy. Twenty consecutive left-side breast cancer patients who underwent breast-conserving surgery were included to the study. For each patient, two different treatment plans were created for the entire breast. FIF plans and CRT plans were compared for doses in the planning target volume (PTV), the organ at risk (OAR) volume including ipsilateral lung, heart, left ascending coronary artery (LAD) and the contralateral breast, the homogeneity index (HI), and the monitor unit (MU) counts required for the treatment. Paired samples t-test was used for statistical analysis. The FIF technique significantly reduced the maximum dose of the PTV as well as the mean doses of the heart, LAD, ipsilateral lung and the contralateral breast (p values were <0.001 for each). When the OAR volumes irradiated with 2, 5, 10, 20, 30 and 40 Gy were compared, the results were in favor of the FIF technique. The volume receiving <20 Gy of the prescription dose for the ipsilateral lung was significantly decreased using FIF technique (p<0.001). FIF technique allowed us more homogenous dose distribution with lower MUs. The FIF technique provided better dose distribution in the PTV and significantly reduced the doses in the OAR. Considering the lower MUs required for treatment the FIF technique seems to be more advantageous than CRT during whole breast irradiation.