Assessment of the prevalence of de novo mutations in the BRCA1 and BRCA2 genes
Department of Pathology Clinical Genetics Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, USA The Royal Marsden Hospital NHS Foundation Trust, London, UK Department of Obstetrics and Gynecology, Northwestern University, Chicago, IL, USA Counsyl, Inc., Redwood City, CA, USA.Clinical Genetics (Impact Factor: 3.93). 07/2011; 80(1):97-8. DOI: 10.1111/j.1399-0004.2011.01691.x
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ABSTRACT: Considering the importance of BRCA1, BRCA2, CHEK2 and TP53 in the development of hereditary early-onset breast and ovarian cancer and that the genetic susceptibility profile of the Northeast population from Brazil has never been analyzed, this study aimed to verify the frequency of mutations of clinical significance in these genes in high-risk hereditary breast and ovarian cancer (HBOC) syndrome patients from that region. DNA samples from 106 high-risk unrelated patients mostly from Bahia, the biggest state in the Northeast region, were analyzed. These patients underwent full BRCA1 gene sequencing, screening for common founder mutations in the BRCA2, CHEK2 and TP53 genes and genetic ancestry analysis with nine ancestry informative markers. The positive results were confirmed by two sequencing reactions. Three mutations of clinical significance were found: BRCA1 p.R71G (4.71%), 3450del4 (3.77%) and TP53 p.R337H (0.94%). The genetic ancestry analysis showed a high European ancestry contribution (62.2%) as well as considerable African (31.2%) and Amerindian (6.6%) ancestry contributions (r2=0.991); this degree of heterogeneity was also significant in the population structure analysis (r=0.604). This population is highly admixed with a different spectrum of genetic susceptibility, with the Galician founder mutation BRCA1 p.R71G accounting for 50% of all identified mutations in high-risk HBOC patients. TP53 p.R337H was also significantly frequent; thus, the combined screening of BRCA1/2 and TP53 should be offered to high-risk HBOC patients from Northeast Brazil.
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ABSTRACT: Early-onset diagnosis is an eligibility criterion for BRCA1 and BRCA2 (BRCA) testing in sporadic breast cancer patients. Limited family structure has been proposed as a predictor of BRCA mutation status in this group of patients. An overwhelming amount of data supports a strong association between BRCA1 mutations and triple-negative breast cancer (TNBC). Here, we analyze the feasibility of using limited family structure and TNBC as predictors of BRCA mutation status in early-onset breast cancer patients attending genetic counseling units. We have conducted the study in a cohort of sporadic early-onset (≤35 years) breast cancer patients (N = 341) previously selected for BRCA genetic testing in Academic Hereditary Cancer Clinics from Spain. A retrospective review of medical records available at the time of risk assessment allowed us classifying patients according to family structure and TNBC. In addition, BRCAPRO score was calculated for all patients. Association between categorical variables was investigated using the Fisher's exact test. Binary Logistic Regression Analysis was used for multivariate analysis. Limited family structure (OR 3.61, p = 0.013) and TNBC (OR 3.14, p = 0.013) were independent predictors of BRCA mutation status. Mutation prevalence in the subgroup of patients with at least one positive predictor was 14 %, whereas it dropped to 3 % in non-TNBCs with adequate family history (OR 5.31, 95 % CI 1.38-23.89, p = 0.006). BRCAPRO correctly discerned between limited and adequate family structures. Limited family structure and TNBC are feasible predictors of BRCA mutation status in sporadic early-onset (≤35 years) breast cancer patients attending genetic counseling units. The low prevalence of mutations observed in non-TNBCs with adequate family structure suggests that this subgroup of patients might be excluded from genetic testing.
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