Genetic Ancestry using Mitochondrial DNA in patients with Triple‐negative breast cancer (GAMiT study)

BACKGROUND Triple‐negative breast cancer (TNBC) lacks estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2)/neu receptors, and is aggressive and therapeutically challenging. Genetic ancestry testing is an emerging medical field. Mitochondrial DNA (mtDNA), which is distinct from nuclear DNA, is maternally inherited and allows for origin determination. Patients with TNBC tend to be younger and are more likely to be African American, making this an ideal disease for mtDNA exploration. To the authors' knowledge, the current study is the first to perform mtDNA for self‐described African American, White, and Hispanic patients with TNBC to identify mtDNA patterns. METHODS Patients with TNBC who were at any stage of therapy/survivorship were included. Self‐reported ethnicity was confirmed at the time of the prospective buccal swab. Haplogroup prediction was performed on sequencing of hypervariable region 1. Using sequence similarity scores and lineage databases, sequence patterns were determined. Data regarding presentation and treatment, tumor features, and outcomes was collected. RESULTS A total of 92 patients were included: 31 self‐described African American, 31 White, and 30 Hispanic individuals. Hispanic patients were found to have the largest tumor size (4.5 cm; P = .01) and youngest age (41 years; P