Radiation-induced fibrosisRadiation-induced fibrosis in the boost area after three-dimensional conformal radiotherapy with a simultaneous integrated boost technique for early-stage breast cancer: A multivariable prediction model

Background and purposeTo develop a multivariable prediction model for the risk of grade ⩾ 2 fibrosis in the boost area after breast conserving surgery (BCS) followed by three-dimensional conformal radiotherapy (RT) with a simultaneous integrated photon boost (3D-CRT-SIB), five years after RT.Material and methodsThis prospective cohort study included 1,030 patients treated with RT for breast cancer (stage 0-III), after BCS. Data regarding physician-rated fibrosis and dose-volume parameters were available in 546 patients. A multivariable logistic regression model for grade ⩾ 2 fibrosis was generated.ResultsAt 5 years, grade ⩾ 2 fibrosis was observed in 13.4% of the patients. The multivariable analysis resulted in a prediction model for grade ⩾ 2 fibrosis in the boost area including three independent variables: patient age, breast volume receiving ⩾ 55 Gy (V55 CTV breast) and the maximum radiation dose in the breast (Dmax).ConclusionsA multivariable prediction model was developed including age, V55 CTV breast and Dmax for grade ⩾ 2 fibrosis in the boost area after breast cancer RT using a 3D-CRT-SIB technique. This model can be used to estimate the risk of fibrosis and to optimize dose distributions aiming at reducing this risk.