Investigation of HBOC germline mutations in women diagnosed with breast cancer in Trinidad and Tobago.

6574 Background: Trinidad and Tobago (T&T) is the southern-most Caribbean island, and according to the WHO/PAHO, it has the 2nd highest breast cancer mortality rate in the region. Notably, a large proportion of breast cancer cases in T&T occur at a young age; with nearly 36% of them being diagnosed under the age of 50. There is a known association between a younger age at diagnosis and Hereditary Breast and Ovarian Cancer syndrome (HBOC). Yet, the prevalence of HBOC mutations remains unknown in T&T, as genetic counseling and testing services are extremely limited in the region. Therefore, we sought to determine the prevalence and spectrum of HBOC mutations in T&T. Methods: At the National Radiotherapy Center, T&T’s main oncology unit, female breast cancer patients, who met NCCN criteria for further genetic counseling and testing were recruited through chart reviews. After pre-test counseling, enrolled subjects had a detailed interview about their personal breast cancer diagnosis and family history. A saliva sample was collected using an Oragene kit, and analyzed by Color Genomics Inc. for 30 genes associated with hereditary cancers. Finalized results were returned to patients by genetic counselors from Color Genomics. Results: A total of 118 female patients who met NCCN guidelines for HBOC testing received genetic testing. A majority were 50 years of age or younger (69/118, 59%). The cohort was ethnically diverse: 34% African, 15% Asian, 48% multiple ethnicity, and 3% other/unknown. A pathogenic or likely pathogenic variant (positive result) was identified in 21.2% of the cohort (25/118) - most commonly identified in the BRCA1 gene (13/25, 52%), followed by BRCA2 (5/25, 20%), PTEN (2/25, 8%), BRIP1 (1/25, 4%), CHEK2 (1/25, 4%), MSH6 (1/25, 4%), PALB2 (1/25, 4%), and RAD51C (1/25, 4%). Conclusions: We found a strikingly high HBOC germline mutation prevalence rate of 21.2% among a cohort of female breast cancer patients meeting NCCN criteria for HBOC testing in T&T. Given the growing implications of germline HBOC mutations for breast cancer treatment and prevention, our results demonstrate an urgent need for funding, as well as the development of robust genetic counseling and testing services in T&T.