Mutation regions mapped on genes that cause breast and ovarian cancer

Where mutations occur in two important cancer genes can affect a woman’s risk of breast or ovarian cancer, a study of thousands of women shows. An analysis of mutations in the BRCA1 and BRCA2 genes reveals that women with breast cancer and women with ovarian cancer harbored mutations in different regions of the genes. The report appears in the April 7 JAMA. 

The biological effect of the specific mutated regions is not yet understood, says study coauthor Timothy Rebbeck, an epidemiologist at the University of Pennsylvania.

Normal BRCA genes encode proteins that are cancer suppressors. The mutated versions confer a high risk of breast and ovarian cancer on women who carry them.

The researchers assembled genetic information from nearly 20,000 women who carried a mutated BRCA1 gene. Of this group, 46 percent had breast cancer, 12 percent had ovarian cancer and 5 percent had both kinds of cancer. The researchers’ dataset also included nearly 12,000 other women who harbored a mutation in the BRCA2 gene. Of those women, 52 percent had breast cancer, 6 percent had ovarian cancer and 2 percent had both.

With further analysis, these differences within the mutated genes might help to predict cancer risk more accurately. “This is part of the precision- and personalized-medicine approach,” Rebbeck says. Some women who harbor BRCA mutations elect to preemptively have their breasts or ovaries removed to prevent cancer. Ultimately, Rebbeck says, a clearer understanding of one’s own genetic mutations might enable a decision based on “better risk numbers.”