Abstract
Germline mutations in BRCA1/2 are the most common cause of hereditary breast and ovarian cancer (HBOC) syndrome. A few studies have reported the prevalence of germline BRCA mutations in Asian patients with breast cancer. Here, we aimed to explore the prevalence and characteristics of breast cancers in Thai patients with germline BRCA1/2 mutations. We retrospectively reviewed breast cancer patients tested for germline BRCA1/2 mutations in our institute during 2014–2018. BRCA mutations were detected using next-generation sequencing and confirmed using Sanger sequencing. We analyzed the characteristics of patients with or without BRCA mutations, disease-free survival (DFS), and associated factors. Among the 67 included patients, 12 (18%) were BRCA1/2 carriers (6 each), 4 (6%) harbored variants of uncertain significance, and 51 (76%) were non-carriers. We discovered two novel frameshift mutations in BRCA2 (c.2380delA and c.8855dupT). Mean ages at breast cancer diagnosis in BRCA1 carriers, BRCA2 carriers, and non-carriers were 39.8, 46.2, and 42.0 years, respectively. The 12 tumors of BRCA carriers were mostly the luminal-B subtypes. Two of these tumors were HER2-positive luminal-B; however, the triple-negative subtype was not observed. After adjusting for stages and luminal subtypes, BRCA carriers experienced worse 3-year DFS than non-carriers (81.5% vs. 90.3%, HR 2.04 (0.64–6.49), P = 0.229). The stage at diagnosis was the sole factor significantly associated with 3-year DFS (100%, 84.8%, and 72.7%; stages I, II, and III, respectively). In summary, breast cancers in Thai patients with germline BRCA1/2 mutations were mostly the luminal-B subtypes and experienced a worse prognosis than those without mutations.