# Prevalence and spectrum of germline BRCA1 and BRCA2 mutations in multiethnic cohort of breast cancer patients in Brunei Darussalam

## TL;DR

This study finds that 5% of Brunei breast cancer patients have BRCA2 mutations, which are more common in Asian populations.

## Contribution

The study is the first to report BRCA1/BRCA2 mutation prevalence in Brunei's multiethnic breast cancer population.

## Key findings

- Three pathogenic and one likely pathogenic BRCA2 mutations were identified in 6 out of 120 patients.
- BRCA2 mutations were more common in Chinese Brunei patients, suggesting a founder effect in Southern Chinese populations.
- BRCA2 carriers had a higher likelihood of family history of breast or ovarian cancer.

## Abstract

This is the first genetic study of its kind in Brunei Darussalam. BRCA1 and BRCA2 genes are the most well-known and well described predictors of hereditary breast cancer due to their clinical importance. This study aimed to identify the prevalence and mutation spectrum of the BRCA1 and BRCA2 germline mutations among 120 unselected series of Brunei breast cancer patients. We screened the entire coding region of BRCA1 and BRCA2 gene using Sanger sequencing and next-generation sequencing methods and identified three pathogenic and one likely pathogenic mutations in the BRCA2 gene. Of the 120 patients, 6 (5%) were BRCA2 carriers which confirm that BRCA2 carriers are more common in the Asian population compared to the Caucasian population. One BRCA2 mutation observed only in the Chinese ethnicity of the Brunei breast cancer population suggest a probability of the mutation being a founder effect in the Southern Chinese population. Brunei BRCA2 carriers were more likely to have a positive family history of breast and/or ovarian cancers and have more than one family members in the first-degree relatives diagnosed with breast cancer.