A recent study demonstrated the validity of current breast cancer testing panels for use in African American women and provides a basis for increased referral of this patient population for cancer genetic testing.
A study, published in the Journal of the National Cancer Institute, identified genes that predispose the African American population to breast cancer.1
Importantly, the study also demonstrated the validity of current breast cancer testing panels for use in African American women and provides a basis for increased referrals of cancer genetic testing in this patient population.
“To the extent that the differences in recommendations are the result of misconceptions among clinicians about the prevalence of genetic mutations and associated risks in African American women, awareness of our findings may serve to increase the proportion of African American women who are offered testing,” corresponding author Julie Palmer, ScD, director of Boston University’s Slone Epidemiology Center and the Karin Grunebaum Professor in Cancer Research at the Boston University School of Medicine, said in a press release.2
Looking at 5,054 African American women with breast cancer and 4,993 unaffected African American women drawn from 10 epidemiological studies, researchers evaluated the associations between mutations in panel-based genes and breast cancer risk. Germline DNA samples were sequenced for mutations in 23 cancer predisposition genes using a QIAseq multiplex amplicon panel.
Overall, pathogenic mutations were identified in 10.3% of African American women with estrogen receptor (ER)-negative breast cancer, 5.2% of women with ER-positive breast cancer, and 2.3% of unaffected women. A higher risk for breast cancer was associated with the BRCA1 (OR, 47.55; 95% CI, 10.43 to >100), BRCA2(OR, 7.25; 95% CI, 4.07-14.12, and PALB2 (OR, 8.54; 95% CI, 3.67-24.95) mutations. Meanwhile, a high risk for ER-negative disease was associated with the RAD51D mutation (OR, 7.82; 95% CI, 1.61-57.42) and a moderate risk for ER-positive cancer was associated with the CHEK2, ATM, ERCC3, and FANCC mutations.
“We also found that mutations in PALB2, RAD51C, and RAD51D confer increased risks of estrogen receptor negative breast cancer in the African American population,” study co-author Fergus Couch, PhD, Zbigniew and Anna M. Scheller Professor Medical Research at Mayo Clinic, said in a press release.
RECQL mutations were associated with risk for all breast cancer types in African American women.
Rates of breast cancer genetic testing are currently substantially lower in African American women with breast cancer than in white women of the same age. This disparity is due, in part, to the differences in recommendations given to African American women, possibly because of misconceptions among physicians about the prevalence of mutations and associated risks in African American women. According to the researchers though, testing for breast cancer predisposition genes can help prevent deaths from breast cancer; both in women who have never had breast cancer and those with breast cancer.
“Depending on results of the testing and an individual’s own weighing of pros and cons, a woman with a mutation in any of these genes may choose more aggressive screening for cancer, and women with mutations in the high risk BRCA1 and BRCA2 genes may choose removal of her breasts and/or ovaries as a way to prevent initial breast cancer or recurrence,” Palmer explained.
Notably, a major limitation of the current study was the sample size. Although there were 5 times as many affected women as in the next largest study of African ancestry breast cancer, the CIs were wide, which prevented certainty about the degree of the associations. However, the inclusion of a sizable number of affected women without a family history of breast cancer was an important strength of the study.
“The present results demonstrate, for the first time, the validity and utility of gene-panel testing, beyond BRCA1 and BRCA2, for breast cancer in (African American) women,” the authors wrote. “Testing will be particularly valuable for women diagnosed with ER-negative and/or (triple-negative breast cancer) and their families.”
1. Palmer JR, Polley EC, Hu C, et al. Contribution of Germline Predisposition Gene Mutations to Breast Cancer Risk in African American Women. J Natl Cancer Inst. doi:10.1093/jnci/djaa040.
2. African American and White Women Share Genes that Increase Breast Cancer Risk [news release]. Boston University. Published May 20, 2020. https://www.bumc.bu.edu/busm/2020/05/20/african-american-and-white-women-share-genes-that-increase-breast-cancer-risk/. Accessed May 28, 2020.