Cutting Genetic Breast Cancer Risk
More Breast Cancer Research Needed on Prevention
Oct. 23, 2003 -- Even the highest risk of breast cancer can be offset by exercise and a healthy weight during teenage years, new breast cancer research suggests.
The study is being called the most comprehensive to date of women with inherited mutations of the BRCA1 and BRCA2 genes. These genes are cancer suppressor genes, and women with mutated forms do not suppress tumor growth and have an increased risk of ovarian or breast cancer. The study appears in this week's edition of the journal Science, and it illustrates the need for more research in breast cancer prevention.
"It was a surprise, but a source of hope, to learn that factors over which we have some control made a difference in the age at which these highest-risk women developed breast cancer," says lead researcher Mary-Claire King, PhD, professor of genome sciences and medicine at the University of Washington in Seattle, in a news release.
"Women with inherited mutations were at extremely high risk, but exercise and appropriate weight during their adolescent years clearly delayed the onset of breast cancer," she says.
Secrets of Teenage Lifestyle
Other breast cancer research has shown wide variations in estimated risk of breast cancer among women with BRCA1 and BRCA2 mutations. Overall, the lifetime risks of women developing breast cancer is about 10%; in women with these mutations the lifetime risk of developing breast cancer is thought to be in excess of 80%.
To better understand this phenomenon, King and her research team looked at a variety of lifestyle factors and the BRCA1 or BRCA2 gene type in more than 1,000 women with a history of breast cancer recruited at 12 major cancer centers in New York City.
Of the 1,008 women found to have breast cancer, 104 had a BRCA1 or BRCA2 mutation.
What the researchers found in this study was that 50% of the women who carried the mutation did not have a history of breast or ovarian cancer in their immediate family because the mutation had come from their father. "If a family is small, there may be no warning that a mutation is present," says King.
The study showed that those with the BRCA1 or BRCA2 mutation had a 20% risk of breast cancer by age 40, a 55% risk by age 60, and more than 80% by age 80 -- an overall 82% risk of cancer in their lifetime, reports King.
But after factoring in exercise and body weight, researchers discovered that these two factors indeed delayed the age of onset of breast cancer in those with the inherited mutations. Those who were physically active developed breast cancer later than those who were physically inactive.
The study also showed that normal weight and lighter weight at age 21 was associated with an older age of breast cancer onset.
Those women who were physically active and kept a healthy weight as teenagers developed breast cancer later than other women, King reports.