Background/Objectives: Late diagnosis hampers effective treatment of non-small cell lung cancer (NSCLC). This study evaluated whether circulating microRNAs (miRs), miR-155 and miR-3196, measured in liquid biopsy peripheral blood mononuclear cells (PBMCs), can serve as potential non-invasive biomarkers for NSCLC diagnosis, patient stratification, therapy monitoring, and prognosis. Methods: RNA was isolated from PBMCs of 136 NSCLC patients and 64 healthy donors. RT–qPCR quantified miR expression in PBMCs after predefined QC filtering: miR-155-3p (NSCLC n = 63; controls n = 28), miR-3196 (NSCLC n = 55; controls n = 28), and miR-155-5p (NSCLC n = 23; controls n = 12). Diagnostic performance was assessed using receiver operating characteristic (ROC) analyses, reporting area under the curve (AUC), and threshold-dependent sensitivity/specificity. Survival was analyzed with Kaplan–Meier/Cox methods. Associations with clinicopathological variables (stage, metastasis, smoking, EGFR, and KRAS status), treatment response (chemotherapy, immunotherapy, TKIs), and survival outcomes were examined. Results: miR-155-3p was upregulated in NSCLC, whereas miR-3196 was downregulated relative to controls; AUCs were 0.881 and 0.784, respectively. At high-sensitivity operating points, specificity was lower (≈29–30%), consistent with PBMC miRs reflecting both immune activation and tumor burden. In adenocarcinoma, miR-155-3p was associated with advanced stage, metastatic disease and smoking history. miR-3196 aligned with features of metastatic progression. During systemic therapy (chemotherapy, immunotherapy, TKIs), circulating levels of both miRs tended to normalize. Notably, normalization of miR-155-3p levels was associated with improved overall survival, supporting its prognostic value and utility for treatment monitoring. Conclusions: Circulating miR-155-3p and miR-3196 in PBMCs are promising screening/monitoring non-invasive candidates rather than stand-alone NSCLC diagnostics at current thresholds. Combining these miRs with additional biomarkers and/or clinical covariates and tuning decision thresholds may enhance specificity for diagnostic use. While preliminary, these findings warrant validation in large, prospective studies with standardized protocols to enable clinical implementation.
Alexandre et al. (Sat,) studied this question.