WEDNESDAY, Nov. 1 (HealthDay News) -- Female relatives of women with mutations in BRCA1 or BRCA2 still have a threefold increased risk of developing breast or ovarian cancer even if they lack mutations in either gene, according to a report published online Oct. 31 in the Journal of Medical Genetics.
D. Gareth R. Evans, M.D., Ph.D., from St. Mary's Hospital in Manchester, U.K., and colleagues studied 277 families with a member carrying mutations in BRCA1 or BRCA2, of which all but six had breast and/or ovarian cancer. Family members were assessed for their cancer risk.
The researchers found that 49 percent of 531 living female relatives tested negative for either the BRCA1 or BRCA2 mutation, or 24 percent of the 118 who had breast and/or ovarian cancer. Of 107 first-degree relatives testing negative, 12.1 percent had breast cancer. For those testing negative for BRCA1 or BRCA2 mutations, the standardized incidence ratio was 3.2 by 50 years of age for first-degree relatives in whose family all other cases of breast and ovarian cancer were explained by the identified mutation.
"In high-risk families, women who test negative for the familial BRCA1/BRCA2 mutation have an increased risk of breast cancer consistent with genetic modifiers," Evans and colleagues conclude. "In light of this, such women should still be considered for continued surveillance."
The authors note that U.S. guidelines state that women whose five-year risk of breast cancer is over 1.7 percent should be screened starting at 35 years of age.
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