Validation of the diagnostic efficiency of folate receptor-positive circulating tumor cells in lung cancers: a prospective observational study

BACKGROUND: This study sought to validate the clinical value of folate receptor-positive circulating tumor cell (FR+CTC) for the diagnosis of lung cancers. METHODS: Seventy-five lung cancer patients and 71 non-malignant participants (including 48 benign lung disease patients and 23 healthy subjects) were enrolled in this study. Three milliliters of the whole blood sample was collected from all the participants (before surgery for cancer patients). FR+CTC analysis was performed using “CytoploRare Detection Kit”. The expression level of serum biomarkers, including carcinoembryonic antigen (CEA), cytokeratin fragment 19 (CYFRA21-1), and neuron-specific enolase (NSE), were also tested in cancer and benign lung disease patients. RESULTS: The median FR+CTC level in lung cancers (10.5 CTC units/3 mL blood) was significantly higher than that of the non-malignant group (5.9 CTC units/3 mL blood, P<0.0001). No significant difference in FR+CTC level was observed between patients with different age, gender, and pathological subtype (P>0.05), except for clinical stage (stages I–III versus stage IV: P=0.0169). With 7.9 CTC units/3 mL blood as the cut-off threshold, FR+CTC showed superior sensitivity (78.7%) and specificity (81.7%) in the diagnosis of lung cancers. The detection rate of FR+CTC was significantly higher compared to CEA (24.0%), CYFRA21-1 (48.0%), and NSE (16.0%). The diagnostic efficiency of FR+CTC was similar in stage I lung cancers (n=25, sensitivity =68.0% and specificity =90.1%). CONCLUSIONS: Our results support that FR+CTC is an independent and efficacious biomarker in the diagnosis of lung cancers. FR+CTC detection can be used to assist in early-stage thoracic cancer diagnosis.