Population-based identification and characterization study of patients at-risk for hereditary breast cancer in in Southern Brazil: Preliminary results

Abstract

9664 Background: Hereditary breast cancer (HBC) accounts for only 5–10% of all breast cancer cases (BC) in most populations. In Rio Grande do Sul (RS), BC is the first cause of all deaths in young women (30–49 years). This study will examine the contribution of genetic risk factors to this observation. Methods: A target sample of all 10,000 women residing in a specific area of Porto Alegre will be characterized for HBC risk factors. Results: Currently, 2500 of these women were recruited and submitted to an HBC risk-questionnaire to assess presence of: a) 1st degree relative with BC and/or OC; b) male relative with BC; c) relative with BC under age 50; d) 2 or more relatives with BC and/or OC; e) relative with bilateral BC; f) relative with both breast and ovarian cancer. Sixteen percent of these women reported at least one of these risk factors and were called for a genetic evaluation. Of these, 118 families were evaluated so far. Regarding specific risk factors, 43% reported at least one 1st degree relative with BC and/or OC; 50% at least one relative with BC before age 50, and 6% at least one relative with bilateral BC. The average lifetime risk of breast cancer for these patients by the Gail and Claus models was 11,34% and 13,73% respectively. The estimated average mutation probability in these genes was 11,77% and 28/118 families (23%) had a >20% chance of carrying a mutation. When criteria for other breast cancer predisposition syndromes was analysed, we found that 6/118 (5%) families fulfilled criteria for the Li-Fraumeni-like syndrome. Finally we compared the lifetime risk estimates for BC obrtained during the initial visit with that obtained after confirmation of family history with medical records. Risk was stratified in three categories: low (< 10%), medium (10–30%), and high (> 30%). In an initial evaluation, risk was as follows: low 63,25%, medium 26,5% and high in 10,25%; after confirmation of family history, these figures were 78,55%, 10,53% and 10,53%, respectively. There was concordance in initial and final risk estimates in 87% of patients. Conclusions: Results of this study will influence the delineation of specific BC prevention strategies for the local community. No significant financial relationships to disclose.