Prevalence of BRCA mutations and founder effect in high-risk Hispanic families.
Approximately 12% of the U.S. population is Hispanic, with the majority residing in urban centers such as Los Angeles. The prevalence of BRCA mutations among high-risk Hispanic families is unknown.


METHODS
One hundred and ten unrelated probands of Hispanic origin, with a personal or family history of breast and/or ovarian cancer, presented for genetic cancer risk assessment, were enrolled in an Institutional Review Board-approved registry and underwent BRCA testing. Haplotype analyses were done if BRCA mutations were observed in two or more unrelated probands.


RESULTS
Mean age at diagnosis was 37 years (range = 23-59) for the 89 (81%) probands with invasive breast cancer. Overall, 34 (30.9%) had deleterious mutations (25 in BRCA1, 9 in BRCA2), 25 (22.7%) had one or more unclassified variants, and 51 (46.4%) had negative results. The mean pretest mutation probability using the Couch model, Myriad model, and BRCAPro was 19.6% (range = 4-77%). The combined average mutation probability was 32.8% for carriers, 15.5% for noncarriers, and 12.9% for variant carriers (P < 0.0001). The most common deleterious mutation was 185delAG (4 of 34, 11.8%). The Hispanic 185delAG carrier families share the same haplotype from D17s1320 through BRCA1, as do two reference Ashkenazi Jewish families. Haplotype analyses of additional recurrent BRCA1 mutations [IVS5+1G>A (n=2),S955X (n = 3), R1443X (n = 3), and 2552delC (n = 2)] also suggest founder effects, with four of six mutations seen almost exclusively in families with Latin American/Caribbean or Spanish ancestry.


CONCLUSIONS
This is the largest study to date of high-risk Hispanic families in the United States. Six recurrent mutations accounted for 47% (16 of 34) of the deleterious mutations in this cohort. The BRCA1185delAG mutation was prevalent (3.6%) in this clinic-based cohort of predominantly Mexican descent, and shared the Ashkenazi Jewish founder haplotype.
Weitzel
Jeffrey N
JN
Department of Clinical Cancer Genetics, City of Hope Cancer Center, 1500 East Duarte Road, Mod 103, Duarte, CA 91010, USA. jweitzel@coh.org
Lagos
Veronica
V
Blazer
Kathleen R
KR
Nelson
Rebecca
R
Ricker
Charité
C
Herzog
Josef
J
McGuire
Colleen
C
Neuhausen
Susan
S
D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D019398:Genes, BRCA1; D024522:Genes, BRCA2; D005838:Genotype; D006630:Hispanic or Latino / Q000235:genetics*; D006801:Humans; D015141:Los Angeles / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D015995:Prevalence; D012042:Registries; D018570:Risk Assessment