August 8, 2014 — Women with mutations in a gene called PALB2 have a 14% chance of developing breast cancer by age 50 and a 35% chance of developing the disease by age 70, according to a new study in the New England Journal of Medicine, MedPage Today reports (Bankhead, MedPage Today, 8/6).
PALB2 is the third gene found to potentially increase the risk of breast cancer. In the mid-1990s, researchers discovered that mutations in the BRCA1 and BRCA2 genes were tied to a heightened risk of the disease (Kelland, Reuters, 8/6). Women with BRCA1 gene mutations have been found to have a 50% to 70% chance of developing the cancer by age 70, while those with the BRCA2 have a risk of 40% to 60%, according to the New York Times. By comparison, the lifetime risk of developing breast cancer in the general population is about 12%.
Previous studies found that PALB2 mutations were linked to breast cancer, but they had not demonstrated the extent that mutations in the gene heightened carriers' cancer risk, the Times reports (Bakalar, New York Times, 8/6).
According to study co-author William Foulkes, about one in 1,000 women have the PALB2 mutation (Thompson, HealthDay/CBS News, 8/7).
For the study, researchers analyzed data from 362 family members with PALB2 mutations, representing 154 families (Reuters, 8/6). The data came from 14 different sites in eight countries.
None of the families carried BRCA1 or BRCA2 mutations, but at least one person in each family had breast cancer and a PALB2 mutation.
The study found that breast cancer risk for women under age 40 with PALB2 mutations was eight to nine times higher than among the general population. Meanwhile, the risk for women ages 40 to 60 with the mutation was six to eight times higher than the general population, while the risk for women over age 60 was five times higher.
The researchers are unsure why younger women with PALB2 mutations appear to have a higher risk of developing breast cancer.
The study also found that women with PALB2 gene mutations had a slightly higher likelihood of developing "triple negative" breast cancer, a form that is more aggressive, more resistant to hormone treatment and more likely to recur (New York Times, 8/6).
The researchers also found that individuals with PALB2 mutations had more than twice the risk of ovarian cancer, compared with the general population (MedPage Today, 8/6).
Certain diagnostic laboratories offer tests to detect the PALB2 mutation. Researchers recommended that women who are found to carry the mutation undergo additional surveillance, such as receiving an MRI breast scan (Reuters, 8/6).
Additional Gene Associated With Breast Cancer Risk
In related news, mutations of the multiple endocrine neoplasia type 1 gene -- or MEN1, which normally acts as a tumor-suppressor -- also increase women's risk of breast cancer, according to a study described in a NEJM letter to the editor, MedPage Today reports (MedPage Today, 8/6).
Although MEN1 mutations were known to lead to a rare form of cancer called multiple endocrine neoplasia, the study is the first to show that those women with the disease also have a more than doubled risk of breast cancer. Researchers noted that because multiple endocrine neoplasia is so rare, the findings are mainly important to women in that population (HealthDay/CBS News, 8/7).