Genetic Risk and Lifestyle
Posted 6/6/2010
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Women who have a positive gene mutation (BRCA1 or BRCA2) sometimes worry if other things in their lives may increase their risk even more. We all wonder about the contribution of lifestyle factors to our breast cancer risk. How much does it really matter if we took HRT or don't exercise or are overweight or drink? Since no one can answer these questions with certainty, it easily becomes one more good way to torture ourselves and raise our anxiety.
My experience has been that most women have a private theory re why they have breast cancer. Whether the "reason" is too much stress or not enough time at the gym, we generally know that is isn't the cause--but keep wondering all the same. My favorite "reason" was one woman who admitted she thought her breast cancer had been caused by her large dog stepping on her breast. Not so. As a reminder, the truth is that although we know there are some risk factors, no one knows what causes an individual woman's breast cancer. It is not something that you did or something that you did not do.
This is all meant as an introduction to a recent article in the New York Times talking about lifestyle factors not raising the risk for women with a positive gene mutation. Here it is:
June 1, 2010
Breast Cancer Genes Not Worsened by Lifestyle
By THE ASSOCIATED PRESS
Filed at 7:04 p.m. ET
LONDON (AP) -- Genes that make women more susceptible to breast cancer don't have any link to lifestyle factors that also raise their risk, a new study says.
Some experts previously thought there might be dangerous interactions between breast cancer mutations and other risk factors for the disease, like taking hormone replacement therapy -- and that these women had a particularly high risk of breast cancer.
According to a study published Wednesday in the medical journal, Lancet, that isn't the case. British researchers studied 7,610 women with breast cancer and 10,196 women without it. All of the women provided a blood sample for genetic testing and information about other risk factors like obesity, alcohol consumption and hormone replacement therapy.
The scientists used a statistical analysis to examine the relationship between genetic and lifestyle factors. They found that although genetic mutations and lifestyle choices both contribute to cancer, they do so separately and do not mix for a more deadly effect.
The genetic mutations studied are carried in up to 60 percent of women and increase a woman's breast cancer risk from 10 to 20 percent. The study did not include the rare BRCA genes which dramatically increase the risk of breast cancer. The study was paid for by Britain's Medical Research Council and Cancer Research UK. Ruth Travis of the Cancer Epidemiology Unit at the University of Oxford and the study's lead author, said it was reassuring she and colleagues didn't find any proof of synergy between breast cancer mutations and lifestyle factors.
''There's a danger of feeling you're at the fate of your genes,'' Travis said. ''But whatever you're born with, there are things you can do to modify your risk.''
Experts said lifestyle factors are often more important in avoiding breast cancer than genetic ones. For example, being fat elevates your risk by 40 percent and taking hormone replacement therapy doubles it.
Susan Gapstur, vice president of epidemiology at the American Cancer Society, said the findings would not change the group's prevention messages to women, like avoiding weight gain, staying physically active, and minimizing hormone replacement therapy. Gapstur was not connected to the study.
She said the research underlined the complexity of breast cancer and that scientists still don't completely understand what triggers it. ''It likely won't be a single genetic factor (that causes breast cancer) but maybe several genetic variants in combination and some environmental factors,'' she said.
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