UC Davis

The immune system continuously interacts with tumors, possibly leading to systemic alterations in circulating immune cells. However, the potential of these cancer-associated changes for diagnostic purposes remains poorly explored. To investigate this, we conducted a comprehensive flow cytometric analysis of 452 peripheral blood mononuclear cell (PBMC) samples from 206 non-small-cell lung cancer (NSCLC) patients, 100 small-cell lung cancer (SCLC) patients, 94 healthy individuals, and 52 benign lung disease (BLD) patients. We focused specifically on circulating T cells, given their close interaction with tumors, and initially assessed 93 T-cell features from the flow cytometric analysis. Using a feature selection protocol, we identified five T-cell features in peripheral blood with strong diagnostic relevance. Notably, while individual alterations in these features lacked cancer specificity, simultaneous alterations were uniquely indicative of lung cancer. To comprehensively analyze these features, we developed a scoring model, IMmunoPhenotypic Analysis for Cancer deTection (IMPACT). Comprehensive analysis using the five features (IMPACT-5) demonstrated high cancer specificity and biomarker efficacy, as evidenced by the high area under the receiver operating characteristic curve values for lung cancer patients (0.9187, 0.9277, and 0.9363 for stage I NSCLC, stage IV NSCLC, and SCLC patients, respectively), in stark contrast to BLD patients (0.5212). These findings suggest that comprehensive analysis of cancer-associated changes in circulating T cells can effectively detect lung cancer from its early stages, proposing immunophenotypic analysis of circulating T cells as an innovative liquid biopsy-based diagnostic biomarker.