Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancer cases and is common in patients under 50. Our retrospective study analyzed the association between pre-treatment circulating microRNA levels in TNBC patients and disease outcome.

The study included plasma samples from the Blokhin National Medical Research Center of Oncology collected before treatment. MicroRNAs were isolated using miRNeasy Serum/Plasma Advanced Kit (Qiagen); reverse transcription and ddPCR were performed using TaqMan® MicroRNA Reverse Transcription Kit, TaqMan® MicroRNA Assay probes (ThermoFisher Scientific), and TaqMan probe mix (RainSure). The results were processed using GeneCount Analysis software (RainSure) and the Hiplot (ORG) cloud service (https://hiplot.cn/).

Four patient groups were identified. Group 1 was characterized by a decreased concentration of miR-124a, miR-137, and miR-148a to 0.0-0.5 copies/μL and included patients aged 40-42 years, T3-T4, N1-N3; regional progression was observed in 67%, and brain metastases were observed in 5% of cases. Groups 2 and 3 were characterized by a gradual increase in miR-124a, miR-137, and miR-148a levels to 5-7 and 7-10 copies/μL and included patients aged 48-67 years; metastasis was absent in both groups, and patients in group 3 did not show disease progression during the 18 months of observation. Patients in group 4 had miR-124a levels of 15-32 copies/μL, miR-137 and miR-148a levels of 7-10 copies/μL, and elevated miR-34c-3p levels (12-17 copies/μL) compared to other groups. There was no disease progression in patients in group 4 over an 18-month follow-up period, and all patients achieved a pathologic complete response following the administration of neoadjuvant chemotherapy.

Analysis of circulating microRNA levels, particularly miR-124a, miR-137, miR-148a, and miR-34c-3p, before treatment can be used to assess the risk of TNBC progression. However, further studies of these microRNA levels in the plasma of healthy volunteers are needed.