Prevalence of mutations linked to breast cancer risk similar between Black, white patients
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Researchers found no clinically meaningful differences in the prevalence of germline pathogenic variants in a dozen breast cancer risk genes between Black and white women with breast cancer, according to a study published in JAMA Oncology.
Results of the case-control, population-based, multicenter study suggested there is inadequate evidence to make policy changes related to genetic testing based specifically on race.
“Prior studies have suggested that Black women with breast cancer were more likely than non-Hispanic white women to have pathogenic variants in breast cancer susceptibility genes. However, these studies were small or had ascertainment bias (for example, including only women who had undergone commercial testing),” Susan M. Domchek, MD, executive director of Basser Center for BRCA, director of the MacDonald Women’s Cancer Risk Evaluation Center and Basser professor in oncology at Penn Medicine, told Healio. “The findings reiterated the importance of making sure all women have equal access to genetic testing. A potential reason that past studies showed that Black women who underwent commercial testing had more mutations than white women is that the Black women had to be at higher risk to get tested. The bar was higher for them to get the testing they needed.”
For the analysis, Domchek and colleagues assessed data of 3,946 Black women (mean age at diagnosis, 56.5 years) and 25,287 non-Hispanic white women (mean age at diagnosis, 62.7 years), unselected for family history or age at diagnosis, from the Cancer Risk Estimates Related to Susceptibility (CARRIERS) consortium, a group of 17 large epidemiology studies focused on women in the general U.S. population who develop breast cancer.
Researchers collected data from June 1993 through June 2020 and analyzed it between September 2020 and February 2021.
They compared the prevalence of pathogenic variants in 12 genes associated with breast cancer risk using Fisher exact test, first among all breast cancer cases combined and then stratified by age (< 50 years vs. 50 years), tumor ER status and separately for women with triple-negative breast cancer.
Among the 12 breast cancer susceptibility genes evaluated, Domchek and colleagues found no statistically significant difference by race in the combined prevalence of pathogenic variants (5.65% of Black women vs. 5.06% of white women).
Among the genes analyzed, researchers found a higher prevalence of pathogenic variants in CHEK2 among white vs. Black women (1.29% vs. 0.38%; P < .001). Black women, however, had a higher prevalence of pathogenic variants in BRCA2 (1.8% vs. 1.24%; P = .005) and PALB2 (1.01% vs. 0.4%; P < .001).
Among women diagnosed before age 50 years, researchers observed no difference in overall pathogenic variant prevalence according to race (8.83% of Black women vs. 10.04% of white women) and only CHEK2 differed in prevalence among individual genes (0.43% vs. 1.82%; P < .001). Additionally, the prevalence of pathogenic variants among women with ER-negative breast cancer did not differ significantly, except for in PALB2 (1.83% vs. 0.95%; P = .04).
The standardized prevalence ratio of pathogenic variants among white women relative to Black women was 1.08 (95% CI, 1.02-1.14) and there was no longer a statistically significant difference in prevalence of pathogenic variants in BRCA2 after researchers adjusted for age at diagnosis.
“Women with breast cancer at younger ages (younger than age 50 years), those with triple-negative breast cancer, and those with a family history of breast cancer or ovarian cancer are at higher risk for having pathogenic variants in high-risk breast cancer genes and should be offered testing regardless of race,” Domchek said.
Because Black women are much less likely to undergo genetic counseling and testing — often due to differences in physician recommendations or access to care — the Basser Center last year launched Black & BRCA, an initiative to provide tailored resources and support to the Black community, according to a press release accompanying the study.
“At a time when Black men and women are more likely to be diagnosed with cancer at later stages when it is less treatable, Black & BRCA seeks to empower people to understand their family health history and take action to prevent cancer from one generation to the next,” Domchek said in the release.
For more information:
Susan M. Domchek, MD, can be reached at Basser Center for BRCA, Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Blvd., Philadelphia, PA 19104; email: susan.domchek@pennmedicine.upenn.edu.
Perspective
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Nicole E. Thompson, MS
The results of this study further emphasize that the field of genetics has work to do when it comes to increasing access to genetic counseling and testing to reach communities of color. Although it is encouraging to learn that studies are showing that race is not a sole factor for the prevalence of breast cancer-related pathogenic germline variants in Black women, it is also disappointing to see the number of Black participants in the study is far lower than that of white women.
The knowledge of one’s carrier status regarding breast cancer predisposition genes is important. It can save lives and improve outcomes. However, this opportunity is lost for Black women who do not receive the chance to be tested. If the prevalence of breast cancer-related genetic predisposition is relatively equal among Black and white women, access to genetics should be as well.
This will provide Black women with the equitable opportunity for medical management options that non-Hispanic white women benefit from more often than any other racial group. Our colleagues should make a concerted effort to connect with organizations and groups that represent and support the health of Black women to increase recruitment efforts for the development of genetic tools and tests.
We should also remove the unencumbered assumption that Black women do not want genetic counseling/testing and instead consider the many complexities that contribute to lower numbers of participation. These include lack of referrals to genetic counseling from physicians, historical medical mistreatment of Blacks, the scarcity of Black genetic counselors, cultural competency barriers, etc. This study should influence how we practice and our outreach strategies.
Race may not be the reason why we should consider practice and policy changes based on the prevalence of pathogenic germline variants, but race consistently proves to be a significant factor that is observed regarding health inequities.
It is concerning that there were almost six times more white women included in this study than Black women, yet it was found that the prevalence of having a breast cancer-related pathogenic variant showed no statistical difference. This shows us that white women are benefiting from knowing their breast cancer predisposition status, whereas Black women are not. Scientific advances will continue to aid in the intensification of health disparities until all populations are equal contributors to the development of genetic tools and tests, involvement in clinical trials, and uptake in genetic counseling and testing. Our current advances will not benefit all populations if they are not reaching all populations.
The next logical steps would involve our colleagues referring all populations for genetic evaluation who meet national/societal guidelines for genetic counseling. This could be aided by the recruitment and retainment of Black genetic counselors, as studies have shown that having a culturally competent genetic counselor significantly increases diverse recruitment into cancer genetic studies and participation in genetic counseling. For context, it would be helpful to observe the frequency of variants of uncertain significance (inconclusive genetic test results) among Black women and white women, as it has been noted that Black women are more likely to receive these inconclusive results, therefore having fewer opportunities to change their management of care.
It is important to note that the Basser Center for BRCA is doing the work to empower the Black community to learn more about their family health histories and providing resources and access to genetics via Black & BRCA. It is through programs like these that we will start to create opportunities for everyone to live their best lives, from one generation to the next.
National Society of Genetic Counselors
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