Dosimetric evaluation of whole breast radiotherapy using field-in-field technique in early-stage breast cancer.

BACKGROUND: The purpose of this study is to evaluate the dosimetric benefits of whole breast radiotherapy (WBRT) using the field-in-field technique compared with conventional tangential field radiotherapy with physical wedges for WBRT.
METHODS: In this planning study, 20 patients were included. For each patient, two different treatment plans were created for the entire treated breast. The dosimetric parameters of the planning target volume for dose evaluation and the organs at risk for each planning technique were compared. In the clinical outcome, acute skin toxicity for each treatment technique was compared.
RESULTS: The field-in-field technique significantly reduced the maximum dose, the volumes receiving >107% of the prescription dose, and homogeneity index for the planning target volume for dose evaluation compared with the tangential field technique. For each dosimetry of the organs at risk, excluding the contralateral breast, the field-in-field technique significantly reduced the maximum dose and the volumes receiving >10, 30, and 50 Gy of the prescribed dose. The volume receiving <1 Gy of the prescription dose for the contralateral breast was significantly decreased using the field-in-field technique. In addition, the dose distribution using the field-in-field technique in the target volume was less sensitive to the effects of breast motion during normal breathing. In the clinical outcome, the field-in-field technique significantly reduced Radiation Therapy Oncology Group (RTOG) grade II acute skin toxicity compared with the tangential field technique (3.1 vs. 10.6%).
CONCLUSIONS: WBRT using the field-in-field technique improved dose distribution in the treated breast and decreased RTOG grade II acute skin toxicity compared with conventional tangential field radiotherapy with physical wedges.