Ethnicity Affects Influence of Breast CA Risk Factors

(MedPage Today) -- Several established breast cancer risk factors are less informative for Hispanic women than for non-Hispanic white women, researchers found.

Among Hispanic women, traditional risk factors could explain only 36.4% of premenopausal cancers and 6.6% of postmenopausal cancers, reported Lisa Hines, ScD, of the University of Colorado at Colorado Springs, and colleagues.

In contrast, 75.4% of breast cancers in premenopausal non-Hispanic white women were associated with traditional risk factors such as reproductive history, family history of breast cancer, menstrual history, hormone use, alcohol consumption, physical activity, height, and body mass index, Hines and colleagues reported online in Cancer.

For postmenopausal non-Hispanic white women, these risk factors explained 62.1% of the observed cancers.

The results "may explain much of the observed differences in breast cancer incidence rates between non-Hispanic white women and Hispanic women," Hines and her colleagues wrote.

"These findings reflect the need for additional studies to gain a better understanding of the factors that influence breast cancer development among Hispanics and in other ethnic and racial populations."

Little research has focused on how ethnic differences in the prevalence of established risk factors, which were identified from studies of primarily non-Hispanic white women, may explain differences in breast cancer incidence, according to the researchers.

So they turned to the population-based, case-control Four Corners Breast Cancer Study, conducted in Arizona, Colorado, New Mexico, and Utah. A third of the nearly 5,000 women in the study were Hispanic. Information on potential risk factors was obtained in structured interviews with participants.

Overall, non-Hispanic white women had higher rates of breast cancer for all age groups, with a widening difference with increasing age.

A comparison of non-Hispanic white women with Hispanic women revealed differences in the prevalence of certain risk factors and in the magnitude and direction of their associations with breast cancer.

Among both premenopausal and postmenopausal women, Hispanics were more likely to report certain characteristics associated with lower breast cancer risk, including younger age at first birth, a greater number of children, shorter height, no oral contraceptive use, and less alcohol consumption.

Premenopausal Hispanic women were more likely to report a higher BMI and postmenopausal Hispanic women were more likely to report menopause at age 50 or younger and no recent hormone therapy use, all factors associated with lower breast cancer risk.

But Hispanic women were more likely to report certain other factors associated with increased risk of breast cancer, including younger age at menarche, not breast feeding, and low physical activity.

For most of the factors evaluated among premenopausal women, the risk estimates (odds ratios) were in the expected direction for non-Hispanic white women, with ORs ranging from 1.23 for low physical activity to 1.97 for a positive family history of breast cancer, although not all were statistically significant.

Among Hispanic women, the associations were either attenuated or not observed. The only factor associated with a significantly increased risk of breast cancer was older age (OR 2.48, 95% CI 1.36 to 4.53).

In general, the findings were similar for postmenopausal women.

Only two factors were significantly associated with breast cancer risk in postmenopausal Hispanic women (MedPage Today) -- family history (OR 1.59, 95% CI 1.13 to 2.25) and height (OR 1.42, 95% CI 1.04 to 1.94).

Regarding the risk factors evaluated in the study, Hines and her colleagues wrote, "We recognize that it is presumptuous to make claims with respect to the proportion of breast cancers that truly are preventable by modifying these factors. Healthy behaviors, such as increased physical activity and decreased alcohol consumption, still should be recommended for Hispanic women."

The Four Corners study was funded by grants from the National Cancer Institute.

The authors did not make any financial disclosures.

Primary source: Cancer Source reference: Hines L, et al "Comparative analysis of breast cancer risk factors among Hispanic and non-Hispanic white women" Cancer 2010; DOI: 10.1002/cncr.25154.