Modeling the risk of secondary lung malignancy in patients treated with breast radiation therapy.

1085 Background: The risk of secondary lung malignancy (SLM) is a concern for women treated with breast radiation therapy after breast conserving surgery for early stage breast cancer. The purpose of this study was to estimate the absolute and relative risks of developing secondary lung malignancies in patients treated either with supine or prone whole breast radiotherapy or with Mammosite brachytherapy. Methods: Twenty-two women treated with breast radiotherapy were enrolled in the study. Fifteen patients underwent CT simulation and standard fractionated and hypofractionated whole breast radiation treatment planning in both the prone and the supine positions. Seven patients underwent CT simulation and treatment planning for Mammosite brachytherapy. Dose-volume histograms of the ipsilateral breast and the lungs were calculated and incorporated into a biologically-based mathematical model of spontaneous and radiation-induced carcinogenesis to quantitatively predict the lifetime absolute and relative risks ...