Dosimetric outcomes of the breast field-in-field (FIF) radiotherapy technique in patients with mastectomy and lumpectomy surgeries

Background: Field-in-field (FIF) technique for treatment of breast cancer has become a widely performed method over the recent years. However, there was no study in the applica on of FIF technique in pa ents with breast cancer undergoing mastectomy and lumpectomy. This study is an a#empt to compare dosimetric outcomes a$er applying the FIF technique in these pa ents. Materials and Methods: Twenty-four pa ents with right and le$ breast cancer par cipated in this study. The FIF planning technique was carried out for pa ents undergoing mastectomy and lumpectomy using the TiGRT treatment planning system (TPS). For the comparison purpose, we used two main indices, i.e. dose homogeneity index (HI) and conformity index (CI), the number of subfields, as well as mean, maximum, and minimum doses, doses received by 2% (D2) and 98% (D98) of the target volume, volumes received greater than 107% (V>107%) and less than 95% (V<95%) of the prescribed dose, doses to organs at risk (OARs), and total monitor units (MUs). Results: The results indicated that CI and HI are be#er in pa ents with right and le$ breast lumpectomy surgery (p<0.038 and p<0.047) rela ve to mastectomy pa ents (p<0.037 and p<0.029), respec vely. Other parameters men oned in Materials and Methods did not show any significant difference between the two groups of pa ents (p>0.05). Conclusion: The use of alterna ve subfields resulted in be#er dose distribu on in target volume with the increase in breast volume. Moreover, to disappear the hot spot areas in isodose curves, it is essen al to elevate the number of subfields.