Abstract P2-07-09: CPM rate among individuals with breast cancer who underwent multiplex gene testing for hereditary cancer: Single institution experience

Background: Availability of multiplex gene (MPG) testing for hereditary cancer has led to increase use of panel testing versus single gene testing for hereditary cancer. These panels include high, but also moderate penetrance genes. For some of these genes, associated cancer risk and risk management guidelines do not exist. Furthermore there is a high rate of variant of unknown significant (VUS) findings in non-BRCA genes. Currently, in the absence or minimal available data, health care providers and patients are faced with important risk management decisions, especially regarding preventive surgeries, such as prophylactic mastectomy. Currently, there is no data regarding prophylactic mastectomy rate among patients with breast cancer who underwent (MPG) testing. Therefore, our aim was to evaluate the rate of contralateral prophylactic mastectomy (CPM) in a cohort of individuals who underwent multiplex gene testing. Methods: Eight hundred thirty five patients with breast cancer who underwent MPG testing between the years 2013 and 2016 were identified using Institutional Clinical Cancer Genetics Database. Patients with pathogenic, likely pathogenic variants or who had a VUS were included in the analysis. Results: Of 835 patients with a diagnosis of breast cancer; 105 (13%) had a pathogenic or likely pathogenic mutation: 29 (28%) BRCA1, 26 (25%) BRCA2, 11 (11%) ATM, 2 (2%) BARD1, 3 (3%) BRIP, 9 (9%) CHEK2, 1 (1%) MSH2, 1 (1%) NBN, 5 (5%) PALB2, 4 (4%) PTEN, 1 (1%) RAD51C, 5 (5%) TP53, 4 (4%) CDH1, 2 (2%) MUTYH, 1 (1%) PMS2, 1 (1%) APC (1). A total of 102 (12%) VUS were found. Average age of diagnosis was 44 (Range 21-81). CPM rate was 32% (n=66) for the total cohort. Twenty nine % (n=19) of patients with non-BRCA mutations, 24.2% (n=16) with VUS and 46% (n=31) with BRCA mutations opted for CPM. Conclusion: Overall 32% of breast cancer patients with germline mutations or VUS opt for CPM at our institution. The rate for CPM in non- BRCA mutations carriers is high despite no available data regarding contralateral breast cancer risk and benefit of CPM. This finding should be validated in larger cohorts, including identification of reasons behind decision for CPM in these cohorts. Citation Format: Elsayegh N, Gutierrez Barrera AM, Kuerer HM, Hernandez ND, Litton JK, Arun BK. CPM rate among individuals with breast cancer who underwent multiplex gene testing for hereditary cancer: Single institution experience [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-07-09.