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Differences in Breast Cancer Risk Factors Among Hispanic and non-Hispanic White Women

The 4-Corners Breast Cancer Study

April 29, 2010

Study Design:  A population-based, case-control study 

Study Eligibility:  Cases included women aged 25 to 79 years at the time of breast cancer diagnosis who were recruited from 4 southwest states (Arizona, Colorado, New Mexico, and Utah). Controls included women younger than age 65 selected randomly from computerized drivers' license lists in Arizona and Colorado and women 65 years or older selected from Center for Medicare Studies lists in all 4 states.   

Enrollment:  536 cases and 493 controls were non-Hispanic women and 321 cases and 323 controls were Hispanic women

The 4-Corners Breast Cancer study was designed to investigate factors that lead to the difference in breast cancer incidence rates observed between Hispanic women and non-Hispanic white women.  The study was a population-based, case-control study of breast cancer.  In this analysis, the researchers evaluated ethnic differences in the prevalence of established breast cancer risk factors and their associations with the risk of breast cancer.  The investigators looked at risk factors such as reproductive history, family history of breast cancer, menstrual history, hormone use, alcohol consumption, physical activity, height, and body mass index.  Cases included women aged between 25 to 79 years at the time of breast cancer diagnosis from 4 southwest states (i.e., Arizona, Colorado, New Mexico, and Utah).  Controls included women younger than age 65 selected randomly from computerized drivers' license lists in Arizona and Colorado and women 65 years or older selected from Center for Medicare Studies lists in all 4 states.         

This analysis included 536 cases and 493 controls that were non-Hispanic women and 321 cases and 323 controls that were Hispanic women.  The estimates of risk for the majority of risk factors were in the expected direction among premenopausal non-Hispanic white women.  Significant positive associations were observed for older age at first birth, not breast feeding, younger age of menarche, and having a positive family history of breast cancer.  Among premenopausal Hispanic women, these associations were not statistically significant or not observed.  Older age at first birth was the only risk factor significantly associated with increased risk among both premenopausal Hispanic and non-Hispanic white women.  For postmenopausal non-Hispanic white women, recent history of estrogen and progestin use, younger age at menarche, and positive family history of breast cancer were significantly associated with increased breast cancer risk.  For postmenopausal Hispanic women, only positive family history of breast cancer and tall height were significantly associated with increased breast cancer risk.

The study findings showed notable ethnic differences between non-Hispanic white and Hispanic women both in the prevalence of risk factors and their associations with breast cancer.  The observed differences in the associations with risk factors as well as the differences in the prevalence of these factors may explain much of the observed differences in breast cancer incidence rates between the two groups.  But additional studies are needed to better characterize and understand the factors that influence breast cancer development in Hispanics and in other ethnic groups.  Also, the study was a population-based, case-control study, prone to bias (such as recall bias and selection bias) and cannot be used to prove causation.  Identifying an appropriate control group is another challenge of case-control studies.  Population controls usually have limited or inaccurate recall of past exposures because they are healthy while cases would be more likely to review their past history in search of a reason for their illness.  

 Click here to read the study abstract.