Women who have excess body weight during the first half of their life may be less likely to develop breast cancer later on, according to one researcher at the University of Massachusetts, who believes this relationship flips after about age 50.
That turning point is menopause, the period in a woman’s life when she stops menstruating.
UMass epidemiologist Susan Hankinson said varying levels of hormones called estrogens and androgens might explain why. Previous studies have found high levels of these chemicals to be associated with increased breast cancer risk.
However, it is unclear which hormone is problematic because androgens can be converted into estrogens with the help of enzymes in the breast.
“We don’t know if it’s really androgens or if the androgens are simply a source, like a depot, of estrogens,” Hankinson said.
Hankinson’s current research aims to answer that question. She will try to tease apart the two hormones by looking at tumor tissue and developing an “expression score” for estrogen and androgen. Based on those scores, she hopes to gain insight into which hormone is more strongly associated with increased breast cancer risk.
One of the goals of the research is to improve the risk prediction models currently available for breast cancer.
“We’re now looking to see if hormones can add to our ability to predict risk,” Hankinson said.
Hormones may also provide an explanation as to how body size and breast cancer risk are related throughout a woman’s lifetime.
Postmenopausal women may be at higher risk because they have higher estrogen levels, Hankinson said. Excess body weight during this time can exacerbate the problem because fat converts androgens to estrogens, which is similar to the process that can occur in the breast.
Hankinson said it is less clear why young, overweight women may be shielded from breast cancer risk. One possibility is that certain hormonal influences may cause the breast tissue to become more resistant to the cancer, “but the specifics of that simply aren’t known yet,” Hankinson said.
But, it would not be appropriate for a young woman to gain weight as a means to lowering her breast cancer risk.
“That would overall be a really bad thing to do,” Hankinson said, as being overweight is associated with other chronic conditions like diabetes and heart disease.
“There are lots of biochemical changes associated with being heavy as a child, and so if we find out what of the underlying biochemistry may be accounting for the association, there may be ways to impact those same biologic pathways,” Hankinson added.
Hormones likely play a key role in breast cancer risk, but Hankinson said lifestyle choices could also have an influence.
Alcohol consumption increases risk while physical activity decreases risk, she said.
“Those are factors that are under a woman’s control that she can actually change to give herself a lower risk profile,” Hankinson said.
Other faculty members in the school of public health are also actively researching breast cancer, including assistant professor Katherine Reeves and associate professor Susan Sturgeon.
“I think women’s health has become a really central focus of the school of public health,” Hankinson said.
Hankinson came to UMass last fall after serving as a professor at Harvard Medical School for about 23 years. She said she was happy to be joining the University at a time when the school of public health was growing in faculty and increasing its emphasis on research.
In addition to conducting research, she teaches an undergraduate public health course called Chronic Disease Epidemiology.
David Barnstone can be reached at firstname.lastname@example.org.