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December 10, 2007
New Calculations Assess Breast Cancer Risk in Black Women
Researchers have devised a new and improved method for calculating breast cancer risk in African American women. The technique, called the CARE model, finds that earlier formulas may have underestimated the odds of black women developing breast cancer.
For more than a decade, many clinicians and researchers have estimated a woman's likelihood of developing breast cancer by using the Breast Cancer Risk Assessment Tool, developed by Dr. Mitchell Gail and his colleagues at NIH's National Cancer Institute (NCI). Physicians use it to counsel patients on their cancer risk. Clinical researchers often use the tool to determine a woman's eligibility to participate in breast cancer prevention trials. However, because it was developed using data primarily from white women, the tool's relevance to other racial groups has been questioned.
In a study published in the December 5, 2007, issue of the Journal of the National Cancer Institute, Gail and collaborators from several institutions developed and tested a new risk-assessment model targeted to African American women. Their updated calculations drew on medical data collected for other large NIH-funded clinical studies.
The researchers analyzed medical data on more than 3,200 African American women, about half of whom had invasive breast cancer. All the women had participated in the Women's Contraceptive and Reproductive Experiences (CARE) study, funded by NIH's National Institute of Child Health and Human Development (NICHD). Using the data, the scientists computed cancer risks based on the women's age at their first menstrual period, the number of mothers or sisters with breast cancer, and other factors. Risk assessments were further refined by including updated national cancer statistics.
The researchers next tested the predictive abilities of the new model by analyzing data from more than 14,000 black women in another NIH-funded clinical trial, the Women's Health Initiative. None of the women had a history of breast cancer when they enrolled in the trial. The CARE model predicted that 323 of the women would develop invasive breast cancer during the follow-up phase of about 8 years. In fact, 350 of the women developed breast cancer as the study progressed — a close match to the CARE prediction.
For black women 45 and older, risk predictions from the CARE model were usually higher than those from the earlier risk assessment tool. As a result, the new model might enhance African American eligibility in breast cancer trials. Using the CARE model, the researchers re-assessed screening data from 20,278 black women who had been considered for a now-completed cancer-prevention trial. The actual trial, using the Breast Cancer Risk Assessment Tool to screen candidates, found that only 14.5% of the black women were eligible to participate. In contrast, when the new CARE model calculated the risk, twice as many African American women, or 30.3%, qualified.
Because of the new method's higher accuracy for African American women, NCI now plans to add the CARE model to its online tools for assessing breast cancer risk. The researchers note that the CARE model should be used with caution or avoided for certain women, like those with a previous history of breast cancer or with specific genetic mutations.