Abstract P4-03-09: Genetic and hereditary factors in breast cancer: Experience in a mastology service on analysis of genetic tests in high risk women
Authors: Chagas SR , Pineres MdRS , Chagas CR , Vieira RJ 
Published: May 2019

Background: Breast cancer is the most prevalent cancer in women in Brazil. The estimate by 2018 is 59,700 new cases. Of these, 10 to 15% are hereditary, caused by mutations in susceptibility genes that increase the risk of disease onset. These types of mutations can occur in several genes, each associated with different risks of developing the pathology. In hereditary breast-ovarian syndrome, the most frequently altered genes are BRCA1 and BRCA2. Mutations of these genes are associated with a 70-85% risk of developing breast cancer during life, but we know that there are other types of genetic alterations at risk of developing breast, ovarian, or other cancers - many are of uncertain significance and others, less known, appear to have high pathogenic potential. Thus, individuals identified with hereditary risk for developing breast or ovarian cancer should have intensive follow-up and genetic counseling.

Materials and methods: A retrospective study was carried out between 2015 and 2018. The charts of each of the patients submitted to genetic counseling with a total of fifteen women were analyzed. Eleven of these, performed genetic tests to evaluate mutations in BRCA1 and 2, and four patients extended panels. Subsequently, a statistical analysis of the data was performed and the results were analyzed thanks to the informed consent that the patients signed.

Results: Among the fifteen cases the age ranged from 27-68 years. Fifteen patients were analyzed, twelve with diagnosis of breast cancer and three without. In the eleven women who tested for BRCA1/2, 27% had mutations for these types of genes and three pathogenic variants of the genes. In the four who did the extended test, three had mutations in six types of genes, two with mutations of uncertain significance(VUS) and one pathogenic variant of the BLM gene. The indications for the exams were: 1)breast cancer patients: five cases with triple negative carcinomas and age less than 60 years-41.66%; 2)four with family history-33.33%; 3)three only by age-25%. In those without breast cancer the indications were family history. The majority of cases were requested for triple negative neoplasia, in which two cases presented mutation(40%) and three cases without mutation(60%), the two mutations in the BRCA1 and BRCA2 genes, one in each of them and none in VUS . In the four cases with a family history, two had mutations and two did not(50%) - two in BRCA 2 and one in VUS. In the three cases without cancer was found mutation in only one of them and with important family history was found mutation in one case(BRCA2).

Conclusions: Mutations in BRCA1/2 genes are associated with susceptibility to develop breast-ovarian cancer. Currently these mutations are responsible for only a minority of familial cases and we also find variants of uncertain and pathogenic behavior. Intensive research to identify other types of genetic mutations that could be responsible for a significant percentage of breast cancer in BRCA1/2 negative families, as well as assessing their importance, appear to be necessary. As already published by other authors, although our casuistry is small, we also call attention to the presence of mutations in young patients with triple negative breast carcinomas.

Citation Format: Chagas SR, Pineres MdRS, Chagas CR, Vieira RJ. Genetic and hereditary factors in breast cancer: Experience in a mastology service on analysis of genetic tests in high risk women [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-03-09.