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BOSTON -- Premenopausal women appear to be developing invasive breast cancer at a greater rate than their grandmothers did, researchers said here.
BOSTON, Nov. 10 -- Premenopausal women appear to be developing invasive breast cancer at a greater rate than their grandmothers did, researchers said here.
And young African-American women are having higher invasive breast cancer rates than white women, added Devra L. Davis, Ph.D., M.P.H., director of the University of Pittsburgh's Center for Environmental Oncology, and colleagues.
Compared with women of their grandmothers' generation, black women had a 41% greater rate of invasive breast cancer and white women had a 21% greater rate, the investigators reported at the American Public Health Association meeting here.
"The good news is that rates of invasive breast cancer are on the decline overall," said Dr. Davis. "However, African-American women, particularly younger women, have not shared in this trend. We need to find out very quickly why this is and take immediate steps to rectify the problem."
She and her colleagues studied trends in invasive female breast cancer, focusing on interracial differences.
At the APHA meeting, and in an article published in Medical Hypotheses, the investigators speculated that "the use of estrogen and other hormone-containing personal care products in young African American women accounts, in part, for their increased risk of breast cancer prior to menopause, by subjecting breast buds to elevated estrogen exposure during critical windows of vulnerability in utero and in early life."
Early and continued exposures to environmental estrogens or estrogen mimics could also account for the greater severity and lethality of breast seen among young women or all races, and among African American women of all races, the investigators speculated.
"We don't know why most women get breast cancer," Dr. Davis said in an interview. "Only one out of 10 or one out of 20 has inherited a germline mutation from her parents, so that means that 19 out of 20 women who get breast cancer get it because of something that happened after they were born."
Most of the known risk factors for breast cancer are hormonally related, she noted, such as age at menarche, childlessness, and excessive alcohol consumption.
In addition "environmental agents that act like hormones -- or in some times are hormones, in the case of placenta -- that are used in personal care products can increase and affect the risk of breast cancer, and African American women do use these products more than others, much more so than white women," Dr. Davis said.
To evaluate trends in invasive (but not non-invasive) breast cancer, the authors obtained data on women regarding black or white race, five-year age group, calendar-year specific invasive breast cancer incidence, and population counts for nine of the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) registries.
"What we did was ask what's the risk of breast cancer for women born in the 1950s or 1960s compared with the risks for their grandmothers, women born at the turn of the century or a little later," Dr. Davis said.
They employed correction factors provided by NCI to correct for reporting delay, and used Poisson age-period-cohort regression models to evaluate the effects of age, birth cohort, and calendar time on breast cancer incidence in black and white women.
They looked at women ages 20 to 39, 40 to 65, and 65 to 84, and grouped them by birth cohort, and looked at incidence rates from 1975 to 2002.
They found that for the more recent birth cohorts, the risks of invasive cancer were about 21% for white women, and about 41% for black women.
"Mammographic screening only became widespread after 1994, and was used more by whites in their 50s than by those in their 60s and older, or by African Americans," the investigators wrote. "This may account for patterns in whites after 1994, but cannot explain patterns in African Americans. Additional research investigating these differences is needed to determine whether avoidable or preventable factors account for some of these patterns and to anticipate demands for health care."
Dr. Davis said that black women may have greater environmental exposure than white to bisphenol A, a plasticizing compound, and to parabens thtat are used in personal care products, drugs, and processed foods.