(ChemotherapyAdvisor) – The largest study of Hispanic breast and/or ovarian cancer families in the U.S. to date has confirmed a 25% prevalence of BRCA mutations, a significant proportion of which were large rearrangement mutations not detectable on standard sequencing, a study concluded in the Journal of Clinical Oncology online December 10.

“Nine recurrent mutations accounted for 53% of the total, suggesting the potential for more cost-effective, ancestry-informed genetic screening,” Jeffrey N. Weitzel, MD, Clinical Cancer Genetics, City of Hope, Duarte, CA, and colleagues noted. “Among these, BRCA1 ex9-12del seems to be a Mexican founder mutation and represents 10% to 12% of all BRCA1 mutations in clinic- and population-based cohorts in the United States.”

The Clinical Cancer Genetics Community Research Network study determined prevalence and type of BRCA1 and BRCA2 (BRCA) mutations among Hispanics in the Southwestern U.S. and their potential impact on genetic cancer risk assessment (GCRA).

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The investigators enrolled 746 Hispanics with a personal or family history of breast and/or ovarian cancer in a registry; each received GCRA and BRCA testing within a consortium of 14 clinics.

In addition, 492 population-based Hispanic breast cancer cases enrolled in the Northern California Breast Cancer Family Registry that were negative by sequencing for BRCA mutations were analyzed for presence of BRCA1 ex9-12del large rearrangement, noted the study investigators.

They detected deleterious BRCA mutations in 189 (25%) of 746 familial clinic patients, 124 BRCA1 and 65 BRCA2; 21 (11%) were large rearrangement mutations, of which 13 were BRCA1 ex9-12del and 1 in BRCA2.

“Regardless of the factors influencing the prevalence and type of BRCA mutations, our study affirms the need for access to BRCA testing for Hispanics, with inclusion of full large rearrangement screening (ie, BART) for all patients,” he stated. “The latter recommendation was included in the 2012 National Comprehensive Cancer Network guidelines, wherein BRCA gene analysis was defined as the combination of sequencing and large rearrangement analyses.”

Sensitivity of a Hispanic-specific BRCA panel is undergoing prospective evaluation.