Breast cancer risk: It’s not all in the family
Women do not automatically have a higher risk of getting breast cancer just because someone else in the family has tested positive for breast cancer genes, U.S. researchers said Monday.
The findings may bring comfort to women from high-risk families after a 2007 study suggested that simply having a relative with a BRCA1 or BRCA2 mutation raised their risk of developing breast cancer, even if they had tested negative for the genes.
“The results are encouraging and reassuring,” said Dr. Allison Kurian of Stanford University School of Medicine, whose study appears in the Journal of Clinical Oncology.
The average woman in the United States has about a 12 to 13 percent chance of developing breast cancer in her lifetime.
Some 5 percent to 10 percent of breast cancers are genetic, and most of these cases are caused by abnormalities in the BRCA1 or BRCA2 genes.
Women with these mutations have a five to 20 times higher risk of developing breast or ovarian cancer, and must undergo intensive cancer screenings and take other precautions to reduce their cancer risk.
Risk Factors for Breast Cancer
In 1940, the lifetime risk of a woman developing breast cancer was 5%, or one in 20. The American Cancer Society estimates that risk to be 13% in 2009, or almost one in eight. In many cases, it’s not known why a woman gets breast cancer. In fact, 75% of all women with breast cancer have no known risk factors.
What Are the Risk Factors of Breast Cancer?
A risk factor is anything that increases a person’s chance of getting a disease. Different cancers have different risk factors.
But having a cancer risk factor, or even several of them, does not necessarily mean that a person will get cancer. Some women with one or more breast cancer risk factors never develop it, while most women with breast cancer have no apparent risk factors.
Significantly higher risk
A woman with a history of cancer in one breast has a 3- to 4-fold increased risk of developing a new breast cancer, unrelated to the first one, in the other breast or in another part of the same breast. This is different than a recurrence of the previous breast cancer.
Moderately higher risk
Getting older. Your risk for breast cancer increases as you age. About 77% of women diagnosed with breast cancer each year are over age 50, and almost half are age 65 and older. Consider this: In women 40 to 49 years of age, there is a one in 68 risk of developing breast cancer. In the 50 to 59 age group, that risk increases to one in 37.
Direct family history. Having a mother, sister, or daughter (“first degree” relative) who has breast cancer puts you at higher risk for the disease. The risk is even greater if your relative developed breast cancer before menopause and had cancer in both breasts. Having one first-degree relative with breast cancer approximately doubles a woman’s risk, and having two first-degree relatives increases her risk 5-fold. Having a male blood relative with breast cancer will also increase a woman’s risk of the disease.
Genetics. Carriers of alterations in either of two familial breast cancer genes called BRCA1 or BRCA2 are at higher risk. Women with an inherited alteration in either of these genes have up to an 80% chance of developing breast cancer in their lifetime.
Breast lesions. A previous breast biopsy result of atypical hyperplasia (lobular or ductal) increases a woman’s breast cancer risk by four to five times.
Many of these women elect to have their breasts or ovaries removed to keep from developing cancer.
Once these mutations turn up in a family, other family members are screened as well. Women from these families who test negative have traditionally been told they have about the same risk as women in the general population.
But a 2007 study published in the Journal of Medical Genetics challenged that notion, suggesting that even though women did not carry the family breast cancer mutation, they still had a two to five times higher risk of developing breast cancer.
Race/Ethnicity
White women are slightly more likely to develop breast cancer than African American, Hispanic, and Asian women. But African American women are more likely to develop more aggressive, more advanced-stage breast cancer that is diagnosed at a young age.
That created a considerable amount of anxiety among doctors and patients, Kurian said in a telephone interview.
To study this, her team analyzed data on more than 3,000 families with BRCA1 or BRCA2 mutations from three countries: the United States, Canada and Australia.
They compared breast cancer rates among carriers and noncarriers of family mutations of the BRCA1 and BRCA2 genes.
They found no evidence of an increased breast cancer risk among women who were noncarriers.
Menstrual History
Women who started menstruating (having periods) younger than age 12 have a higher risk of breast cancer later in life. The same is true for women who go through menopause when they’re older than 55.
“It’s reassuring that we don’t see a signal for elevated breast cancer risk from women who test negative for a familial mutation,” Kurian said.
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By Julie Steenhuysen