Genetic tests may miss BRCA mutations in Latinas, study says

January 11, 2013 | by Hiu Chung So

Many diseases are caused by both genetic and environmental factors, but for many breast and ovarian cancers, mutations in the BRCA genes drastically shift the blame to genetics. Women with these mutations face a five- to 30-fold increased risk of developing such cancers – compared to women without the mutations – and their risk of developing breast cancer can be as high as 85 percent over their lifetime.

 

Mutations in the BRCA1 and BRCA2 genes are linked to substantially higher risk of developing breast, ovarian cancers. Mutations in the BRCA1 and BRCA2 genes are linked to substantially higher risk of developing breast and ovarian cancers.

 

These mutations are relatively rare in the general population, but now researchers have found a "high prevalence" of the mutations among Latinas. The report was published in the Jan. 10 issue of Journal of Clinical Oncology.

The study analyzed data from 746 Hispanic women with a personal or family history of breast or ovarian cancer. All were enrolled in the  Clinical Cancer Genetics Research Network, a collaborative group of more than 30 sites in the United States and Mexico.

Among the women, 25 percent had a BRCA gene mutation. Further, some of those mutations – "rearrangement mutations" – may not be detected by standard genetic tests.

Other findings: 

•11 percent of the women had  large rearrangement mutations, which may be overlooked by basic sequencing screenings.

•15 percent of BRCA1 carriers had mutations also seen in the Ashkenazi Jewish population and may represent a legacy of religious persecution and the Spanish Inquisition, leading Jews to emigrate to the Americas.

• 10 to 12 percent of BRCA1 carriers had a mutation called BRCA1 ex9-12del that is of ancient Mexican origin.

• Nine recurrent mutations, most of Spanish origin, are recurrent across 53 percent of cases.

Lead author Jeffrey Weitzel, M.D., director of the Division of Clinical Cancer Genetics, said that this and other studies “established unequivocally that Latinas with a family history of breast or ovarian cancer should undergo genetic cancer risk assessment.”

Weitzel also encourages at-risk Latinas to seek out a more comprehensive genetic test than is often conducted, one that screens for large rearrangement mutations. Weitzel currently sits on the National Comprehensive Cancer Network’s genetic/familial high-risk assessment panel for breast and ovarian cancers, which also supports the more sophisticated screening process for higher-risk women.

Lastly, because this study identifies recurrent mutations in the Latina population, the results can be used to develop a cost-effective genetic test that screens for these mutations in the BRCA genes.

“Screening for just a handful of the most commonly seen mutations rather than over a thousand of them makes genetic testing much more efficient and affordable,” Weitzel said. “Thus, we can make this vitally important tool available to underserved populations, regionally and globally, that may not have had access to them before; this allows more women to be aware of their risk and take appropriate preventive measures such as more frequent surveillance and prophylactic surgery.”

For more information about genetic screening for cancer, visit City of Hope’s Cancer Screening & Prevention Program page.

This study is supported by grants 1R03CA139588 and 1RC4CA153828 from the National Cancer Institute and grant RSGT-00-263-01 from the American Cancer Society

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