BRCA detection rate in an Italian cohort of luminal early-onset and triple-negative breast cancer patients without family history: when biology overcomes genealogy.

Abstract BACKGROUND: NCCN Guidelines recommend BRCA genetic testing in individuals with a probability >5% of being a carrier. This analysis aimed to evaluate the rate of BRCA mutations in triple-negative breast cancer (TNBC) patients diagnosed ≤60 years and luminal-like breast cancer (BC) patients diagnosed ≤35 without breast and/or ovarian family history. METHODS: 159 TNBC patients diagnosed ≤60 years and 109 luminal-like BC patients diagnosed ≤35 years without family history were retrospectively identified. Mutation prevalence and clinical-pathological characteristics associated with mutational status were evaluated. RESULTS: In TNBC patients, BRCA mutation prevalence was 22.6% (21.4% BRCA1 and 1.2% BRCA2). BRCA1-related TNBC patients were younger (p <0.001). Mutation prevalence was 64.2% ≤30 years, 31.8% in patients aged 31-40, 16.1% for those aged 41-50 and 7.9% for those between 51 and 60 years of age. A total of 40% of patients with estrogen receptor (ER) 1-9% were BRCA1 carriers. BRCA detection rate in early-onset BCs was 6.4% (1.8% BRCA1 and 4.6% BRCA2). Mutation prevalence was 0% 0-25 years, 9% 26-30 years and 6% 31-35 years. BRCA2-positive luminal-like early-onset BCs were more likely associated with low progesterone receptor (PR) expression (p = 0.049). CONCLUSIONS: BRCA genetic testing is recommended in TNBC diagnosed ≤ 60 years, regardless of cancer family history, histotype and by using immunohistochemical staining <10% of nuclei for both ER and/PR as a cut-off. In luminal-like early-onset BC patients, a lower BRCA detection rate was observed, suggesting a role for other predisposing genes.