Circulating Free miRNAs as Liquid Biopsy Biomarkers for Early Detection of Breast Cancer in Peruvian Women

Background: Breast cancer is the most common cancer in women both in Peru and worldwide. Although mammography remains the standard for early detection, its effectiveness may be limited by unequal access to this technology. In this context, liquid biopsy emerges as a minimally invasive complementary technique that allows the identification of circulating biomarkers, such as microRNAs (miRNAs), whose differential expression has been associated with breast cancer. Methods: The present study evaluated the diagnostic potential of cell-free circulating miRNAs for the early detection of breast cancer. In the screening phase, seven candidate miRNAs were quantified by qPCR in plasma from patients with early-stage breast cancer and healthy controls. In the validation phase, miR-191, miR-182, miR-335, and miR-125b were analyzed in an independent cohort of 30 untreated patients to evaluate their diagnostic performance. Results: miR-125b and miR-335 showed the best individual diagnostic performance, with AUCs of 0.81 and 0.78, respectively, and presented a significant moderate correlation (ρ = 0.608; p < 0.05), supporting their biological consistency and potential as complementary biomarkers. The multivariable binary logistic regression model that integrated both miRNAs showed a moderate improvement in discriminatory ability; however, the expanded multivariable model that incorporated the four validated miRNAs achieved an AUC of 0.91, with a sensitivity of 92% and a specificity of 90%. Conclusions: The panel composed of miR-191, miR-182, miR-335, and miR-125b represents a promising set of circulating biomarkers for the early detection of breast cancer.