GlossMagazineOnline (GMO): How long did this study take to complete?
Dr. Julie Palmer: This report was based on data from the Black Women’s Health Study (BWHS). The BWHS has been in progress since 1995 when 59,000 black women enrolled in the study by completing mail questionnaires. It took 14 years of follow-up to collect the data and about a year to classify the cases by hormone receptor status and carry out statistical analyses of the data.
Palmer: The primary impetus was the realization that estrogen-receptor negative breast cancer is about twice as common in women of African ancestry compared with all other population groups in the U.S. and has a worse prognosis, but little is known about risk factors for the disease.
GMO: It has been previously believed that having multiple children decreases the risk of breast cancer in women. Is this belief now inaccurate?
Palmer: This is still true when you look at risk of all types of breast cancer combined across the life course. This is because having multiple children decreases the most common subtype of breast cancer—estrogen-receptor positive breast cancer. There is an initial small increase in risk following childbirth, but as time passes, there is reduction in risk. Since about 60 percent of breast cancers in black women and about 80 percent in white women are estrogen-receptor positive, most studies find a reduced risk of breast cancer after age 50 in women who have had two or more births. However, our study indicated that having more births increases risk of estrogen-receptor negative breast cancer. This is important because estrogen-receptor negative cancers are more difficult to treat and have a higher mortality.
GMO: Why are African American women more likely to develop the aggressive type of breast cancer more than any other race?
Palmer: We do not know why. Possible explanations are genetic differences and differences in immune response.
GMO: What is that type of breast cancer?
Palmer: Breast tumors that do not have receptors for hormones, such as estrogen and progesterone. They are not responsive to treatments such as Tamoxifen.
GMO: Why does breastfeeding decrease the risk of developing this type of breast cancer?
Palmer: We do not know why. One possibility is that when a woman breastfeeds, postpartum involution (the return of the breast to its pre-pregnancy state) happens in a slower, more orderly process, and thus, there may less of the immune system/inflammatory processes that can lead to tumor initiation.
GMO: By what percentage does breastfeeding decrease black women’s chance of getting breast cancer?
Palmer: In our study, black women who breastfed had a 20 percent reduction in risk of getting estrogen-receptor negative breast cancer compared with women who had the same number of births but had never breast fed.
GMO: What do you think could be done to encourage more black women to breastfeed their newborns?
Palmer: Societal changes would help. Many women need to return to work within weeks after giving birth. If women were given paid maternity leave for a longer period, it would be easier to breastfeed. At the least, we need to see changes in workplaces so that new mothers are given a clean, private space to pump their breasts and a refrigerator space to store the milk. Cultural considerations are important too. People don’t change habits just by hearing advice from doctors or other professionals. Many of us learn from our friends and families. I would like to see education programs that use a woman-to-woman approach.
GMO: Are you and your team planning to continue this study?
Palmer: Yes. BWHS participants complete questionnaires every two years and report on new disease diagnoses, such as breast cancer, lupus, diabetes and fibroids. We have a lot more to learn from this study. With regard to estrogen-receptor negative breast cancer, we are teaming with researchers at two other centers who have also been studying breast cancer in black women. By pooling our data, we will have enough cases to make some significant advances in learning about causes of this condition. Knowing the causes opens the way for preventive measures.