Indications for intensity modulated radiation therapy using field-in-field and electronic compensator for the treatment of large left breast volumes

Abstract

Introduction Breast cancer is the most commonly treated cancer at the National Center for Cancer Care and Research in Qatar for which different radiotherapy (RT) techniques have been developed recently. Purpose To evaluate three RT techniques for large left sided breast cancer patients; the 3D wedges technique using Varian Enhanced Dynamic Wedge™ (3DW), the forward planning IMRT with field in field (FIF) and the forward planning IMRT with electronic compensator (EComp) using the Varian multileaf collimator. Materials and methods Thirty patients were included in our study. Treatment plans were created and compared according to dose volume histogram in terms of dose homogeneity within the target volume and dose to OARs as well as conformity indices. Coverage improvement of FIF and EComp over 3DW was also quantified using dose improvement index. Results Target volumes receiving 95% of the dose for the PTV were equal to 89.0 ± 4.1, 94.2 ± 2.19 and 96.8 ± 0.98 for 3DW, FIF and Ecomp respectively. Average value of the dose improvement index was equal to 8.92% and 5.97% for EComp and FIF respectively. No statistically significant difference in lung and heart sparing was observed. An advantage of FIF and EComp over 3DW was observed in the sparing of the contralateral breast. Conclusion EComp and FIF proved to be superior to the 3DW technique with regard to improving dose homogeneity within the PTV and dose to normal tissues. Results showed that EComp is superior for a PTV volume ⩾1500cc, or a separation ⩾25 cm, or a combination of PTV volumes ⩾1200cc and separation ⩾22 cm. Disclosure Authors have nothing to disclose.