Changes in breast cancer incidence rates in the United States by histologic subtype and race/ethnicity, 1995 to 2004.

Breast cancer incidence rates rose throughout the 1980s and 1990s in the United States but have recently declined through 2004. Studies reporting this decline primarily attribute it to the sharp decline in menopausal hormone use following publication of the Women's Health Initiative trial results. However, they have not stratified rates by either histologic type or race/ethnicity, which could further inform contributors to these trends. Using data from 13 cancer registries that participate in the Surveillance, Epidemiology, and End Results program, we evaluated annual percent changes (APC) in breast cancer incidence rates from 1995 to 2004 by histologic type and race/ethnicity for intervals identified using joinpoint regression. Invasive ductal carcinoma and invasive lobular carcinoma incidence rates fell steadily from 1998 to 2004 [APC, -3.07% (95% confidence interval, -4.10 to -2.02) and APC, -3.18% (95% confidence interval, -5.18 to -1.03), respectively]. Declines in rates of breast cancer overall and invasive ductal carcinoma were primarily limited to women > or = 50 years of age and to non-Hispanic whites and Asian/Pacific Islanders, and declines in rates of invasive lobular carcinoma were primarily limited to non-Hispanic whites. The majority of these declines began around 1998 and all began before 2002 when the Women's Health Initiative trial results were published; thus, the abrupt decline in hormone therapy use starting in 2002 is unlikely to be primarily responsible for the recent decline in breast cancer rates. The declines observed thus far are likely attributable to saturation of screening, although further declines related to the widespread cessation of hormone use may follow.