BACKGROUND: The use of liquid tissue, such as circulating cells, to predict treatment response is attracting more attention. OBJECTIVE: The aim of this study was to evaluate association between circulating markers and treatment response. METHODS: One hundred and twelve advanced pulmonary adenocarcinoma patients who were going to receive epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) were included. Tumor tissue and plasma specimens were collected before treatment and analyzed for EGFR mutation and plasma IL-6 and IL-8. Pre-treatment peripheral blood CD146+/CD3- cells (as circulating endothelial cells, CECs), CD34+/CD45- cells (as endothelial progenitor cells, EPCs), and CD133+ cells (as cancer stem cells, CSCs) were measured with flow cytometry. RESULTS: The progression-free survival (PFS) was significantly longer in patients with low CEC, low EPC, and low CSC counts than in those with high cell counts (p < 0.001, 0.041, and 0.001, respectively). Multivariate analysis showed that mutant plasma EGFR (pEGFR) was a poor prognostic factor in EGFR-mutated patients (p = 0.048), and there was a tendency for EGFR mutation-negative patients with high IL-6 level to have worse overall survival (p = 0.051). CONCLUSIONS: CECs, EPCs, CSCs, and mutant pEGFR are useful predictive biomarkers of EGFR-TKI treatment efficacy. IL-6 may predict prognosis in advanced lung cancer.
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