A multicenter clinical trial of lung cancer circulating tumor cell assay with the largest sample size (1210 cases) in China

Background: As a novel biomarker of primary tumors, circulating tumor cells (CTCs) are well known to play an important role in cancer diagnosis, recurrence and metastasis, and disease monitoring. This study investigated the application of CTCs in lung cancer therapy by quantitative determination of folate receptorpositive CTCs. Methods: This study enrolled 1210 subjects (including 560 lung cancer patients, 350 patients with benign lung diseases, 150 healthy subjects and 150 nonlung cancer malignant tumor patients) and quantified the tiny amounts of CTCs in peripheral blood by negative enrichment using immunomagnetic beads in combination with folate receptor-directed polymerase chain reaction (PCR). Results: Following ROC curve analyses of CTC levels in the patients with benign lung diseases or benign lung diseases and the healthy subjects, the cut-off of CTCs was 8.70 CTC Units/3mL with a specificity of 88.2% (441/500) and a sensitivity of 79.6% (446/560) as determined by the method mentioned above. The ROC area under curve of more than 0.8 (AUC = 0.8797, P<0.0001) suggested the excellence of liganddirected PCR to diagnose lung cancer. For stage I-IIV lung cancer patients, the sensitivities were 70.8%(34/48), 79.6% (125/157), and 90.2% (185/205) respectively, and the sensitivity in stage I patients can reach up to 68.0% (102/150) as well. CTC levels appeared to have greater accuracy to diagnose lung cancer (AUC: 0.8833, P<0.0001) than the combination of the other four lung cancer-specific serum tumor markers (CEA, NSE, CYFRA21-1 and SCC)(AUC: 0.8557, P<0.0001). CTCs were related to tumor stage and tumor size other than pathological type. By quantitative determination of folate receptorpositive cells in 150 different types of cancers, the CTC level in lung cancer was found to be higher than those in gastric, breast, colorectal, liver, and esophageal cancers. Conclusions: LT-PCR achieves quantitative determination of folate receptorpositive CTCs to diagnose lung cancer with high sensitivity and specificity, and significantly greater diagnosis accuracy than the model of combined lung cancerspecific serum tumor markers.