Cancer in the Contralateral Breast after Radiotherapy for Breast Cancer

To the Editor: In the March 19 issue, Boice et al.¹ present data to indicate that radiotherapy for breast cancer contributes little to the already high risk of a second cancer in the opposite breast. They note, however, that the risk was significantly increased among women who underwent irradiation at a relatively young age (<45 years). They estimate that the average dose of radiation to the contralateral breast among the exposed women was 2.82 Gy. This average dose exceeds that in other reports² and may reflect technical factors such as the orientation of the anterior internal mammary field and the…