Women With BRCA Mutation Might Have Lower Breast Cancer Risk Than Previously Thought, Study Says

Main Category: Breast Cancer
Also Included In: Genetics
Article Date: 10 Jan 2008 - 5:00 PDT

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Women who have the BRCA1 or BRCA2 genetic mutations might have a lower risk of breast cancer than previously thought, according to a study published Wednesday in the Journal of the American Medical Association, the Wall Street Journal reports.

For the study, Colin Begg, chair of epidemiology and biostatistics at Memorial Sloan-Kettering Cancer Center, and colleagues conducted interviews and independent tests for the genes among about 1,400 women with cancer in one breast and 700 women with cancer in both breasts. The study found that women who had a BRCA1 or BRCA2 mutation had a 40% to 51% risk of developing breast cancer by age 70, compared with the previously cited risk of 50% to 80%. Women had a higher risk of developing breast cancer if a relative was diagnosed with the disease at a young age or had cancer in both breasts, according to the study (Chase, Wall Street Journal, 1/9).

Among women with cancer in one breast, 5.2% had a BRCA mutation, including 42 with a BRCA1 mutation and 31 with a BRCA2 mutation. Among women with cancer in both breasts, 15.3% had a BRCA mutation, including 67 with a BRCA1 mutation and 41 with a BRCA2 mutation. The study found significant differences in the breast cancer risk of women whose families carried BRCA mutations.

The National Cancer Institute, which sponsored the study, estimates that between 5% and 10% of women in the general population carry a BRCA mutation. Ashkenazi Jews have been found to have a higher prevalence of the mutations (Brown, Reuters Health, 1/8). Begg estimates that about 0.5% of U.S. women, or about 750,000 women, have a BRCA mutation.

Screening for BRCA mutations is recommended only for women in families already affected by the disease. The test -- which can cost about $3,000 -- usually is covered by insurance if a woman has family risk factors for the disease. Begg, who said he has no ties to companies that test for the mutations, predicted that screening for the mutations will increase as technology advances and costs decrease (Wall Street Journal, 1/9). Begg added that further research needs to be done to determine the "extent to which risk varies depending on which of these mutations is present in the carrier" (Reuters Health, 1/8).

Comments

"The estimate of 50% to 80% breast cancer risk from the gene is too high," Begg said, adding that "even 40% may be overestimate." According to the Journal, the risk could be overestimated because studies have focused on families known to be affected by breast cancer and have not sampled families not affected by the disease. "My fear is once you're designated a carrier, you clue into this belief that your risk is high," Begg said, adding, "My point is that, if we do population screening, we shouldn't be giving them that 80%."

A spokesperson for Myriad Genetics, which markets a test for the mutations, said the company believes "that high risk is high risk, whether 57% or 87%, and women should know in order to take appropriate actions" (Wall Street Journal, 1/9).

The study is available online.

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