Test African Americans for BRCA Mutations

OB/GYN News,  Jan 15, 2000  by Barbara Baker

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SAN FRANCISCO -- Genetic counseling and testing for BRCA2 and BRCA2 mutations is appropriate for African Americans with early-onset breast cancer or strong family histories of breast or ovarian cancer, Deborah McDermott said at the annual meeting of the American Society of Human Genetics.

More than 10% of such women may have pathogenic BRCA1 or BRCA2 mutations and an even higher percentage may have genetic variants of uncertain significance, said Ms. McDermott, a genetic counselor at Memorial Sloan-Kettering Cancer Center, New York.

Most of the cancer families involved in the effort to identify the BRCA1 and BRCA2 genes were of white, European origin. Subsequent studies on groups at risk for BRCA mutations have also been primarily conducted among whites, Dr. McDermott observed.

She and her associates looked specifically at BRCA genetic test results in African Americans who had either early-onset breast cancer or a strong family history of breast and/or ovarian cancer.

Seven of 59 (12%) subjects from 59 families tested for BRCA1 had discreet pathogenic mutations. An additional 17 (29%) subjects had other BRCA1 sequence variants of uncertain significance.

Among the 38 individuals from 37 families who underwent BRCA2 testing, 2 had pathogenic mutations (5%) and an additional 23 (61%) had variants of uncertain significance.

Both genes were analyzed in 38 individuals. Five of the participants (13%) had pathogenic mutations of at least one gene, and 26(68%) had at least one variant of uncertain significance.

Counseling of high-risk African Americans before they undergo testing should include a discussion of the high likelihood of finding a sequence variant of uncertain significance, Ms. McDermott said.

"There is circumstantial evidence that suggests most of the variants of uncertain significance are benign polymorphisms, some of which may be population specific," she added.

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