Women in BRCA families also have high cancer risk
LONDON (Reuters) - Women with close relatives with breast cancer who do not have the main genetic mutations linked to the illness still has a higher than average risk of developing the disease, UK doctors said on Tuesday.
Even if they test negative for the BRCA1 and BRCA2 mutations, they are three times more likely to be diagnosed with breast cancer by the age of 50 than other women.
"Despite the fact they have not inherited the BRCA 1 or BRCA2 faults, they have a risk of inheriting other genetic faults, many of the genes of which we have not identified," said Professor Garth Evans, of St. Mary's Hospital in Manchester.
"Their chances of developing breast cancer under 50 were three times that in the general population," he told Reuters.
Although the raised risk is relatively small, a rise from 2 percent to 6.4 percent, Evans suggested women in families with a history of breast cancer should be given extra screening for the disease at a younger age -- probably starting at 35 years old.
Genetic mutations account for about five percent of breast cancer cases in developed countries. Although changes in the BRCA1 and BRCA2 genes are the leading known causes, scientists suspect there are many more genes involved.
"We now know there may be 40 or 50 genes that increase breast cancer risk," Evans said. "We are only dealing with the two that are the tip of the iceberg but underneath there is a whole raft of other genetic faults that may only slightly increase your risk."
He and his team tested for genetic faults in 531 close relatives, mainly sisters and daughters, of 277 women with breast, ovarian or both cancers.
About half of the women had negative results for the BRCA1 and BRCA2 faults, including 28 who developed breast cancer and 4 who were diagnosed with ovarian cancer.
The researchers, who reported the findings in the Journal of Medical Genetics, said the phenocopy is probably due to other alterations, or modifier genes, that mimic the changes produced by the specific genetic mutation.
"It is clear it is not the simple story of you either carries a high-risk gene or you don't. It is a spectrum of risks due to a whole host of genetic factors," said Evans.
"Even when you are in a high-risk family with BRCA1 and BRCA2, you still have to take into account these other genetic factors that may be in those families," he added.
Breast cancer is the most common cancer in women, with more than a million cases detected worldwide each year, according to the International Agency for Research on Cancer in Lyon, France.
What breastcancer.org says about this article…
Women in BRCA families also have high cancer risk
The results of this study are particularly important for women with a family member who has an abnormal BRCA1 or BRCA2 gene. Even though these women haven't tested positive for an abnormal BRCA1 or BRCA2 gene, their breast cancer risk was about 6%, which is higher than women who have no family members with an abnormal BRCA1 or BRCA2 gene (their risk is about 2%).
Still, the breast cancer risk in women with a family member with an abnormal BRCA1 or BRCA2 gene (and who haven't inherited the gene themselves) is low compared to women who have inherited an abnormal BRCA1 or BRCA2 gene. Women who have an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70.
Earlier research has shown that genetic testing can miss some abnormalities. If you have a family member with an abnormal BRCA1 or BRCA2 gene or have a strong family history of breast cancer and you don't have an abnormal BRCA1 or BRCA2 gene, talk to your doctor about steps you can take to reduce your risk.
We eagerly await a time very soon when testing for hereditary breast cancer is even more accurate, reliable, and informative. For now, it is important to discuss any family history of breast or other cancers with your doctors. Together you can decide what you and your family can do to protect yourselves against this disease.
