Familial Breast Cancer: Risk to the Contralateral Breast

Pathology reports of 198 familial breast cancer patients were reviewed to determine chronologic features of tumorigenesis in the breast contralateral to the site of initial mastectomy. Actuarial data revealed two major risk periods with a prolonged intervening postoperative gap in which no malignant tumors of the contralateral breast were detected. The cumulative cancer risk to the contralateral breast increased annually at 2.8% in the first 6 postoperative years, then showed no increase in the next 7 years, and finally resumed its upward climb at an accentuated annual rate of 6.8% between years 13 and 16 (inclusive). The corresponding annual rates of increase for second primary breast cancer in the two risk periods were 1.6 and 5.9%, respectively. A total of 37 patients manifested bilateral breast cancer, of whom 21 had pathologically confirmed second primary carcinomas, i.e., primary tumors of the contralateral breast. Of these patients, 27 exhibited a relatively short interval between mastectomies (x=1.7 yr), whereas 10 had a much longer disease-free period (x=16.5 yr). It is likely that tumors manifested in the contralateral breast within 6 years of the initial breast cancer were already developing but were not clinically discernible at the time of first mastectomy. In contrast, the extended disease-free period of many patients suggests that host defense mechanisms may have been stimulated by the first tumor, which in turn had a persisting suppressive effect on de novo carcinogenesis in the contralateral breast. Our results underscore the need for vigorous cancer surveillance of long-term survivors of an initial breast cancer, particularly in familial patients.