Negative BRCA test doesn’t mean you can’t get breast cancer
A new study finds that a negative BRCA test doesn't necessarily mean you will never develop breast cancer.
Just because you test negative for a family-specific BRCA2 mutation, it does not mean that breast cancer is not possible in the future. That's the message behind a new study published in Cancer Epidemiology, Biomarkers & Prevention.
It's known that women with certain mutations in their BRCA1 or BRCA2 genes have a greater risk for breast cancer, but those that test negative for their specific family BRCA mutation are still at risk, the study showed.
"We found that women who test negative for family-specific BRCA2 mutations have more than four times the risk for developing breast cancer than the general population," said Gareth R. Evans, M.D., an honorary professor of medical genetics and cancer epidemiology at the Manchester Academic Health Science Center at the University of Manchester in the United Kingdom. "We also found that any increased risk for breast cancer is largely limited to BRCA2 families with strong family history and other genetic factors."
A negative test result isn't an all-clear
He says physicians should be cautious when telling a woman who has had a negative test that her cancer risk is similar to the general population. That may not be true for women from BRCA2 families that have a strong family history of the disease.
Evans evaluated data from the M6-Inherited Cancer in England study to draw the conclusion. Out of 807 BRCA families, the researchers identified 49 women (or phenocopies) who tested negative for the family-specific BRCA mutation yet wound up developing breast cancer anyway. Of those 49, 22 were among 279 women who tested negative from BRCA1 families, and 27 were among 251 women who tested negative from BRCA2 families. In different age ranges (30-39, 40-49, 50-59 and 69-80), the scientists noted that there were about twice as many breast cancer victims compared to the number expected in the general population.
"It is likely that these women inherit genetic factors other than BRCA-related genes that increase their breast cancer risk," he explained. He noted that approximately 77 single nucleotide polymorphisms (SNPs) — which are genetic variations that can pinpoint the inheritance of disease genes within families — are tied to developing breast cancer. To understand why some women who have had negative tests are at a higher risk, researchers should identify more SNPs, Evans said.
The authors note that specialists should use caution when stating that a woman's breast cancer risk is the same as that of the general population following a negative test, because it may not be true for some women who come from BRCA2 families with a strong family history.