Prevalence of Breast Cancer-Susceptibility Genes Similar in Black and White Women

NEW YORK (Reuters Health) – There is no meaningful difference in the prevalence of pathogenic variants in 12 cancer-susceptibility genes between U.S. Black women and non-Hispanic white women with breast cancer, according to a large population-based study.

As Dr. Susan M. Domchek of the University of Pennsylvania, in Philadelphia, told Reuters Health by email, “The prevalence of genetic mutations associated with breast cancer in Black and white women is the same.”

In a paper in JAMA Oncology, Dr. Domchek and colleagues note that Black women are more likely to be diagnosed with breast cancer before the age of 50 or with estrogen-receptor (ER)-negative and triple-negative breast cancer (TNBC).

“It remains unclear,” they go on to say, “whether these disparities are related to racial differences in germline genetic pathogenic variants (PVs) in breast cancer susceptibility genes and if race should inform strategies for genetic testing.”

To investigate further, the researchers examined data from the CARRIERS consortium population-based studies covering 1993 to 2020. These involved nearly 4,000 Black women with a mean age at diagnosis of 57 years and more than 25,000 white women with a mean age at diagnosis of 63 years.

Twelve established breast-cancer predisposition genes were evaluated: ATM, BARD1, BRCA1, BRCA2, CDH1, CHEK2, NF1, PALB2, PTEN, RAD51C, RAD51D and TP53. There was no significant difference in their combined prevalence, amounting to 5.65% in Black women and 5.06% in white women (P=0.12).

The prevalence of PVs in CHEK2 was significantly higher in white than Black patients (1.29% vs. 0.38%). Meanwhile, Black women had a higher prevalence of PVs in BRCA2 (1.80% vs. 1.24%) and PALB2 (1.01% vs. 0.40%).

For ER-negative breast cancer, the only significant difference in prevalence of PVs was in PALB2, which was higher in Black women. In those diagnosed before the age of 50 years, there was no difference in overall prevalence of PVs and among individual genes, only CHEK2 PV prevalence differed by race.

Although the prevalence of PVs in three genes CHEK2, BRCA2 and PALB2 differed statistically significantly between the two populations, the absolute differences were small, the researchers emphasize.

After adjustment for age at diagnosis, the standardized prevalence ratio of PVs in white relative to Black women was 1.08 (95% confidence interval, 1.02 to 1.14), and there was no longer a statistically significant difference in BRCA2 PV prevalence.

“Continued efforts to promote uptake of and reduce barriers for genetic testing for Black women are warranted,” the researchers observe, but given these findings “we do not see evidence that race should be used as an independent consideration for genetic testing.”

“Despite a similar prevalence of mutations,” Dr. Domchek added, “it has been previously described that Black women are much less likely than non-Hispanic white women to undergo genetic testing. Instead of focusing on differences in rates of mutations, we need to focus our efforts on decreasing disparities and improving access of testing.”

SOURCE: JAMA Oncology online May 27, 2021.

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