The new findings may have clinical implications. “A Hispanic woman who is found to carry any of the CHEK2 variants that we have characterized here, or the PALB2 variants in particular, has enough risk to warrant the addition of breast MRI as a screening tool on an annual basis starting between age 30 and 35, because these cancers can be earlier at onset as well as more likely to occur,” Dr Weitzel said. “Second, we would say that for the PALB2 variant, the risk may be high enough to offer a woman who has a strong family history of breast cancer and this variant to get a risk-reduction mastectomy — a preventive mastectomy.”

Finally, patients in both groups may benefit from potentially using tamoxifen as a means of reducing the risk of breast cancer, he said.

In another study, researchers looked at the genetic data from 77,900 women with breast cancer who had received germline multigene panel testing at the genetic-testing company Ambry Genetics between March 2012 and December 2016.6 The group included 57,003 non-Hispanic white; 6722 black; 5194 Hispanic; 4183 Asian; and 4798 Ashkenazi-Jewish women. The researchers compared the prevalence of gene mutations in these populations. The scientists also assessed associations between mutations in each gene with breast cancer risk.

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The researchers found that certain gene mutations were more or less common among the different populations. For example, BRCA1 mutations were more frequent in all minority populations in the study compared with white women. CHEK2 mutations were, on the other hand, less frequent in all minority populations compared with white women. “If you were to test a racial or ethnically diverse population, the frequency of germline mutations is different between different races and ethnicities. That was one of the major findings that we observed,” said lead study author Siddhartha Yadav, MD, a hematology/oncology fellow at the Mayo Clinic, Rochester, Minnesota.

The researchers also found that mutations in BRCA1, BRCA2, and PALB2 were significantly associated with a high risk of breast cancer across the different populations (odds ratio >4). RAD51C mutation was on the other hand associated with a moderate risk of breast cancer in white women (odds ratio [OR], 1.8), and a high risk of the cancer in black women (OR, 8) and Hispanic women (OR, 13), Dr Yadav said. It is not clear why the degree of risk for this particular mutation differs between these groups. But it could have something to do with potential other genetic differences that are not being captured in the current study, Dr Yadav said. Another possible explanation could be the influence of environmental factors, he noted.

Dr Yadav said that the new results should inform how women of different ethnicities are counseled. Furthermore, he called for updating the current genetic guidelines to reflect the differences in the frequency of certain mutations and mutation-related cancer risk between races and ethnicities. “I think it’s also important to recognize that the current genetic testing guidelines do not really take race or ethnicity into account apart from genetic testing for Ashkenazi-Jewish individuals,” he said. “So I think these guidelines will need to be updated to incorporate race and ethnicity into counseling for genetic testing and counseling for risk of breast cancer.”

Allison W. Kurian, MD, MSc, an associate professor of medicine and of health research and policy at Stanford University School of Medicine, California, who was not involved in either of the two studies, found the results of both studies important, especially given the scarcity of this type of research in diverse populations. “I think it’s really important to drill down and understand better the spectrum of cancer risk in all racial-ethnic groups,” she said.

There are disparities in who gets tested, though, which partially explains why reference genomes may not be as applicable to those with diverse backgrounds. “The proportion of women who should undergo testing and have not done that is much higher in minority populations compared with whites,” Dr Yadav said.

For Hispanic women, issues with access, limited awareness, and language barriers are some of the factors that contribute to these disparities, said Alejandra Hurtado de Mendoza, PhD, an assistant professor at the Cancer Prevention and Control Program at Georgetown Lombardi Comprehensive Cancer Center in Washington, DC. Dr Hurtado de Mendoza specializes in designing interventions that aim to reduce these disparities. For example, Dr Hurtado de Mendoza and her colleagues developed a culturally targeted video recorded in Spanish, in which the main character, named Rosa, chooses to undergo genetic testing about a year after being diagnosed with breast cancer at age 49 years.7 Through her interactions with family and other characters, Rosa serves as a role model and shows women how to overcome barriers to genetic cancer risk assessment. 

Another intervention involves delivering genetic counseling in Spanish by phone (ClinicalTrials.gov Identifier: NCT03959267). One advantage of this approach is eliminating the need to arrange childcare or transportation to meet a counselor in person, Dr Hurtado de Mendoza said. An additional benefit is an opportunity to address the shortage of Spanish-speaking counselors. “If you do it by phone, then you are increasing the reach of those few Spanish-speaking counselors and overcoming the problems with interpretation,” Dr Hurtado de Mendoza said.

Finally, Dr Hurtado de Mendoza and her colleagues are in the process of adapting and testing an intelligent tutoring system called “BRCA-gist” for Hispanic and black women at risk for hereditary breast or ovarian cancer (ClinicalTrials.gov Identifier: NCT03511690). The primary goal of the intervention, which provides information on cancer and genetic testing, is to increase the uptake of genetic counseling in these populations.

References

  1. American Cancer Society. Cancer facts & figures for Hispanics/Latinos 2018-2020. Atlanta: American Cancer Society, Inc. 2018. 
  2. Chlebowski RT, Chen Z, Anderson GL, et al. Ethnicity and breast cancer: factors influencing differences in incidence and outcome. J Natl Cancer Inst. 2005;97(6):439-448. 
  3. Saulsberry K, Terry SF. The need to build trust: a perspective on disparities in genetic testing. Genet Test Mol Biomarkers. 2013;17(9):647–648
  4. Weitzel JN, Clague J, Martir-Negron A, et al. Prevalence and type of BRCA mutations in Hispanics undergoing genetic cancer risk assessment in the southwestern United States: a report from the Clinical Cancer Genetics Community Research Network. J Clin Oncol. 2013;31(2):210-216
  5. Weitzel JN, Neuhausen SL, Adamson A, et al. Pathogenic and likely pathogenic variants in PALB2, CHEK2, and other known breast cancer susceptibility genes among 1054 BRCA-negative Hispanics with breast cancer [published online June 17, 2019]. Cancer. doi: 10.1002/cncr.32083
  6. Yadav S, LaDuca H, Polley E, et al. Racial and ethnic differences in the results of multigene panel testing of inherited cancer predisposition genes in breast cancer patients. Presented at: 2019 American Society of Clinical Oncology (ASCO) Annual Meeting; May 31-June 4, 2019; Chicago, IL. Abstract 1514.
  7. Hurtado de Mendoza A, Graves KD, Gómez-Trillos S, et al. Developing a culturally targeted video to enhance the use of genetic counseling in Latina women at increased risk for hereditary breast and ovarian cancer [published online May 18, 2019]. J Community Genet. doi: 10.1007/s12687-019-00423-w