June 19, 2007 (Insidermedicine) Women with fewer older female relatives are more likely to have the breast cancer gene mutation BRCA, according to a report published in the Journal of the American Medical Association.

Having the BRCA1 or BRCA2 gene mutations increases a woman’s risk of breast cancer by up to 85% and ovarian cancer by as much as 50%. Identifying women who have had BRCA-associated breast cancer is important because they have an increased risk of re-developing breast cancer within 10 years following the initial diagnosis. Effective screening of these patients allows doctors to offer appropriate advice; however, identifying patients with a genetic cancer risk is challenging.

The general consensus is that BRCA testing is not appropriate for unaffected women in the general population, but the guidelines are less clear for women with early onset breast cancer and no family history of breast or ovarian cancer. 

To better understand the inheritance pattern of BRCA-associated breast cancer, researchers studied more than 1,500 women seen at a clinic for genetic cancer risk assessment and BRCA testing, over a 10-year period.  Of these, just over 300 women had breast cancer before age 50 and no close relatives with breast or ovarian cancer.

It was found that half of the women had “limited family structure” – that is, less than two females who lived to age 45 years or more in each lineage. BRCA gene mutations were detected in 14% of participants with a limited family structure compared to 5% of those with a larger family structure. Those with a limited family structure had an increased likelihood of being carriers of a BRCA mutation that those from larger family structures.

While current technology and knowledge may make it simpler to identify the genes of breast and ovarian cancer among women, it is also important to follow the trail among more distant relatives, including the men in the family, since it is likely that half of the BRCA gene mutation carriers are men. 

Given the effectiveness of risk-reducing surgery in women with BRCA-associated cancer, the findings highlight the need to consider heredity when deciding to offer BRCA gene mutation testing to families with a single case of early-onset breast cancer.

Reporting for Insidermedicine, I’m Dr. Susan Sharma.