Gene mutations found in 22% of African American breast cancer patients
CHICAGO – BROCA, a genetic screening panel that combines BRCA1 and BRCA2 testing with screening for all 18 known breast cancer genes, detected at least one loss of function mutation in 56 of 249 unrelated African American women with breast cancer.
African American women are disproportionately affected by early-onset and triple-negative breast cancers, possibly because of a higher frequency of inherited mutations in DNA repair pathways. The finding of abnormalities in 22% of these women represents the first comprehensive screen of all known breast cancer susceptibility genes using next-generation sequencing in African American women, according to Dr. Jane E. Churpek, who reported the results at the annual meeting of the American Society of Clinical Oncology.
These high carrier frequencies suggest the importance of screening for all gene mutations in African American breast cancer patients who are diagnosed at a young age, have a family history, or have triple-negative breast cancer. The results should be used to encourage testing of at-risk family members to identify those who would benefit from lifesaving interventions, said Dr. Churpek of the University of Chicago.
In the 249-patient study, inherited damaging mutations were seen in 44 of 144 patients with a family history and in 12 of 145 women without a family history of breast and ovarian cancer. Of the 67 women who had triple-negative disease, 20 (30%) had mutations; in the 146 women under age 45, 67 (27%) had mutations.
"Even in the absence of triple-negative disease and family history, there are patients with gene mutations," she said.
While the majority of the 56 women with mutations were positive for BRCA1 (26 patients) or BRCA2 (20 patients), other inherited mutations detected in the BROCA panel were found in 10 patients. Those mutations included CHEK2 (n = 3), PALB2 (n = 3), ATM (n = 5), and PTEN (n = 1), she reported. The study population consisted of women who were treated at the University of Chicago cancer risk and breast cancer clinics.
Having an all-encompassing test like BROCA would allow women to undergo a single test, Dr. Churpek said. Further, advances in technology via targeted genomic capture and next generation sequencing allow this test to be performed inexpensively using 3 mcg of peripheral blood. The current clinical approach to testing requires BRCA1 and BRCA2 testing (BRACAnalysis, Myriad) and possible further testing via a genetic panel, which can be expensive and sometimes difficult to get covered by payers, Dr. Churpek said.
She said there are no plans to market the BROCA test, however. Myriad Genetics holds the U.S. patent on the BRCA genes in the context of cancer diagnostics until 2015. The U.S. Supreme Court is considering the legal issues surrounding the gene patent in the case of Association for Molecular Pathology v. Myriad Genetics. Oral arguments in the case were heard in April, and a decision from the court is expected before July.