Carriers of Breast Cancer Gene at Risk of Second Cancer

Dec. 9, 2011 (San Antonio) -- Women who have been successfully treated for cancer in one breast and who carry the BRCA1 or BRCA2 cancer gene are at increased risk for developing cancer in their other breast.

Women who received their first diagnosis when they were 40 or younger and women with so-called triple-negative breast tumors that are often difficult to treat are at particularly heightened risk, says Alexandra J. van den Broek, MSc, a doctoral candidate at the Netherlands Cancer Institute in Amsterdam.

The study involved more than 5,000 women diagnosed with breast cancer before they turned 50; 211 were carriers of the BRCA1 or BRCA2 mutations. Over a nine-year period, 9% developed cancer in their other breast.

Women who were not carriers faced a 6% risk of developing cancer in their other breast over 10 years, compared with 11% for BRCA2 carriers and 20% for BRCA1 carriers.

The 10-year risk shot up to 26% for carriers diagnosed with their first breast cancer when they were 40 or younger.

Those with the BRCA1 or BRCA2 gene with a triple-negative first tumor had a 10-year risk of 19%.

Discussing the Options

Five to 10% of breast cancers occur in women with a genetic predisposition for the disease, usually due to mutations in either the BRCA1 or BRCA2 genes. The lifetime risk of breast cancer increases from 13% to 81% for BRCA1 carriers and 85% for BRCA2 carriers.

Beverly Moy, MD, MPH, a breast cancer specialist at Massachusetts General Hospital in Boston, says women who are BRCA carriers have two basic options. They can get a double mastectomy to substantially lower their risk, but this surgery doesn’t completely eliminate the risk. Or a woman may choose more intense screening with breast MRI in addition to mammography; if cancer does develop, it is typically picked up at an earlier stage, she says.

"Going forward if you are a carrier [of the BRCA1 or BRCA2 gene] and have cancer in one breast, it makes sense to address the risk of cancer in the second breast posed by the study," Moy tells WebMD.

She says she wouldn't change practice on the basis of one study.

"But this is a conversation we are already having with our patients. So if a carrier is young or has triple-negative disease, it makes sense to discuss the potential advantage of a [double] mastectomy approach rather than screening," Moy says.

These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.