ABSTRACT
Breast cancer incidence increases with age and exhibits a Black-to-White crossover around age 45. Breast cancer survivors are at a significantly elevated risk of developing a second primary breast or gynecological cancer compared with the general population. The purpose of this study was to determine whether a similar crossover occurs in hormonally related second primary breast, endometrial, or ovarian cancers in Black and White women. The Surveillance, Epidemiology, and End Results' Registry 9 was used to follow 415,664 White and 39,887 Black female breast cancer survivors, diagnosed at age 19 or older, for a second primary breast, endometrial, or ovarian cancer between 1973 and 2007. Cumulative incidence curves were generated; Pepe and Mori's test was used to test for significance. Second primary breast cancer followed the incidence pattern of the first primary breast cancer in Black and White women diagnosed before age 45. It was opposite of the pattern of first primary breast cancer in Black and White women diagnosed at age 45 or later. Second primary endometrial and ovarian cancers paralleled the incidence pattern of first primaries of the same anatomic site among Black and White women, independent of the age at diagnosis of the first primary breast cancer. Despite the Black-to-White crossover of first primary breast cancer around age 40, the incidence of hormonally related second primaries does not appear affected by the age at diagnosis of the first primary.
