Pathoepidemiological patterns of contralateral breast cancers in Black and White women.

Abstract

10628 Background: Women with one primary breast cancer are at greater risk for developing a second cancer in the contralateral breast, despite the protective effect of Tamoxifen treatment. Breast cancer incidence exhibits a Black-to-White incidence crossover at age 40. The purpose of this study was to investigate whether the patho-epidemiological patterns of second primary contralateral breast cancers in Black and White women are similar to those of the first primary tumors according to age at diagnosis of the first primary breast cancer. Methods: The Surveillance, Epidemiology, and End Results’ (SEER) Registry 9 database was used to follow a total of 455,551 women, 415,664 White (91.24%) and 39,887 Black (8.76%) female breast cancer survivors, diagnosed at age 19 or older, for the occurrence of a second primary contralateral breast cancer between 1973 and 2007. Black and White women with a first primary in-situ or invasive breast cancer and a second primary contralateral breast cancer were analyzed by age at diagnosis, histologic tumor type, histological grade, tumor size, tumor markers, and number of positive lymph nodes. The cumulative incidence of a second contralateral breast cancer, which accounts for the competing risks of death and second non-breast cancers, was also explored among Black and White breast cancer survivors. Results: Second contralateral breast cancers in Black women were characterized by an earlier onset (Blacks= 59 yrs; Whites=67 yrs), higher incidence (Blacks= 8. 7%, 95% CI = 8.3– 9.1; Whites= 7.7%, 95% CI=7.6 - 7.8) and more aggressive clinical presentation than in Whites. In contrast to first primary breast cancers, second primary breast cancers are more common in Black than in White women of all ages. Conclusions: Our results point to the possible bilaterality of many cases of breast cancer, and to a possible shared etiology between cancers in the two contralateral breasts.