CHAPEL HILL -- Screening for mutations in a gene known as BRCA1 that is believed to predispose women to breast cancer should not be done routinely because the mutations are less prevalent than researchers thought, according to a new study.
Widespread screening of breast cancer patients or unaffected women in the absence of family history would waste considerable money and is more likely to yield results that are hard to interpret, say scientists at the universities of North Carolina at Chapel Hill and Washington at Seattle. Testing may be helpful for women from families in which both breast and ovarian cancer have occurred or in which at least four cases of breast cancer have been identified.
"Women who inherit an altered form of this gene from either parent are at increased risk of breast cancer sometime during their lives," said Dr. Beth Newman, assistant professor of epidemiology at the UNC-CH School of Public Health. "Most previous comparable research took place among patients attending specialized cancer clinics so it was estimated that between 11 percent and 20 percent of women carried a defective gene. We found the frequency of breast cancer due to BRCA1 to be considerably lower than that."
For the first time, Newman and colleagues studied women with breast cancer who were not selected on the basis of their age at diagnosis or their family medical history to develop a better estimate of how common mutations in the gene were. Included were 211 N.C. breast cancer patients, ages 20 to 74, and 188 women without the illness who served as controls. About half the subjects were white, and about half were black.
A report on the findings appears in Wednesday's (March 25) issue of the Journal of the American Medical Association.
Besides Newman, a member of the UNC Lineberger Comprehensive Cancer Center and lead investigator, authors include Drs. Robert C. Millikan and Patricia G. Moorman, assistant professors of epidemiology at UNC-CH and Yale University, respectively, and graduate student Lesley M. Butler. Drs. Hua Mu and Mary-Claire King of the University of Washington at Seattle also participated.
The study involved screening the entire sequence, or structure, of the BRCA1 gene in patient blood samples to determine the prevalence of mutations. They found 3.3 percent of white patients carried the mutation, and no black patients did. Overall, 2.6 percent of subjects were carriers.
As expected, the research showed that inherited BRCA1 mutations were more common in high-risk families -- those in which several women had developed breast or ovarian cancer. In white women, the prevalence of inherited mutations was 23 percent for cases with family histories of ovarian cancer, 13 percent for cases from families with at least four cases of breast cancer and 33 percent for cases from families with both breast and ovarian cancer and at least four affected relatives.
"We conclude that widespread screening for inherited susceptibility to breast cancer is just not warranted yet," Newman said. "It makes sense only in very select subgroups."
A special concern is that women who carry a mutated form of BRCA1 may be denied health or life insurance or jobs if it becomes known they are carriers, she said. Being a carrier does not necessarily mean a woman will develop breast cancer even though the gene boosts her chances.
King, Newman and others then at the University of California at Berkeley mapped the BRCA1 gene in 1990. University of Utah and National Institute of Environmental Health Sciences researchers cloned the gene about four years later.
The researchers now are studying the prevalence of a second breast cancer gene called BRCA2. Scientists suspect other breast cancer genes exist but have not found them yet. The National Institutes of Health supports the studies.
The above story is based on materials provided by University Of North Carolina At Chapel Hill. Note: Materials may be edited for content and length.
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