Breast cancer rates may be declining overall, but affluent white women are seeing the most significant declines, according to a new study published in the American Journal of Public Health.
Breast cancer rates declined by as much as 10% annually among white, non-Hispanic women, 50 and older, who live in prosperous countries and who have the kind of tumors that an estrogen-rich environment will nourish, according to lead study author Nancy Krieger, Ph.D., a professor in the department of society, human development, and health at the Harvard School of Public Health (AJPH, February 10, 2010).
The study used data obtained from 13 U.S. population-based cancer registries from 1992 to 2005, and analyzed trends among 350,000 cases, looking at race/ethnicity and socioeconomic position, as well as age at diagnosis and breast cancer tumor characteristics.
The researchers took into account that in 2002, a Women's Health Initiative (WHI) study prompted many doctors to stop prescribing hormone therapy when that study's findings contradicted the previously held assumption that estrogen/progestin replacement therapy would lower a woman's risk of heart disease. Instead, the WHI study suggested that hormone therapy would actually increase the risk of heart disease and breast cancer.
Although Krieger's study did not have access to information on individual women's hormone therapy use, the same group of women who exhibited the most significant decline in breast cancer rates was also the group most likely to have been taking hormones before the WHI study, according to Krieger.
"The recent decline in U.S. breast cancer incidence was not equally beneficial to all women, but instead mirrored the social patterning of hormone therapy use," Krieger wrote. "Joint information on socioeconomic resources and race/ethnicity is vital for correctly understanding disease distribution, including that of breast cancer."
Related Reading
U.S. cancer rates continue their decline: report, December 8, 2009
Breast cancer care delayed for African-Americans, October 27, 2009
ACS report: Breast cancer death rate dropping, September 30, 2009
Cancer rates and related deaths drop in U.S., November 26, 2008
Falling breast cancer rates seen only in whites, April 17, 2008
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