The location of contralateral breast cancers after radiation therapy

Radiation therapy following conservative surgery results in scattered radiation to the contralateral breast, with higher doses to the medial breast and lower doses laterally. The purpose of the current study is to determine whether the location of contralateral breast cancers developing following breast conserving surgery and radiation is indicative of radiation-induced malignancies. The charts of 1,755 patients treated with conservative surgery and radiation therapy between 1970 and 1998 were reviewed. Fifty-nine patients who developed a contralateral malignancy following conservative surgery and radiation therapy and who had complete information and documentation of the location of the second lesion served as the primary focus of the current study. The location of the contralateral malignancy was compared with the location of the primary tumors of the overall patient population. The location of breast cancers developing in the contralateral breast following breast conserving therapy and radiation was not consistent with radiation-induced malignancies. Specifically, there was not a preponderance of medially located tumors in patients developing contralateral breast cancers following radiation. There was a slight excess of central lesions that cannot be explained by higher doses of radiation. The location of breast cancers in the contralateral breast following conservative surgery and radiation is not indicative of radiation-induced lesions. These data should be reassuring to women considering breast conserving surgery and radiation.