B-360 Usefulness of the Ratios of CYFRA21-1 and p53 Autoantibody Immune Complexes to Their Free Antigens in Lung Cancer

Abstract

Abstract Background Autoantibodies against specific cancer-associated antigens are produced in the early stages of tumorigenesis. In lung cancer, the possibility of autoantibodies as diagnostic biomarkers has been proposed. This study was to evaluate the usefulness of novel DNA-guided sandwich immunoassay detecting CYFRA21-1 and p53 autoantibody immune complexes and their free antigens in diagnosis of lung cancer. Methods In total, 100 patients with lung cancer and 119 healthy controls were analyzed with 9G testTM Lung/Cancer (Biometrix Technology, South Korea) measuring plasma autoantibody immune complexes (CYFRA21-1 with anti-CYFRA21-1 autoantibody immune complex (CIC), p53 with anti-p53 autoantibody immune complex (PIC)) and their free antigens (CYFRA 21-1 and p53). The ratios of CIC to CYFRA21-1 (CIC/CYFRA21-1) and PIC to p53 (PIC/p53), and the multiplication of the two ratios, named as LC index were calculated. Results The levels of CIC and PIC were significantly increased in lung cancer compared with those in healthy control (P = 0.0062 and P = 0.0026, respectively), while free antigens didn’t distinguish between lung cancer and healthy control. The ratios CIC/CYFRA21-1 and PIC/p53 were significantly higher in lung cancer than those in healthy control (all, P < 0.0001). Diagnostic performances expressed as area under the curve (AUC) were higher in the ratios of autoantibody immune complexes to each free antigen (PIC/p53 and CIC/CYFRA21-1) than autoantibody immune complexes (PIC and CIC) (AUC; 0.887, 0.847 vs 0.618, 0.608, respectively). The most excellent diagnostic performance was proven with LC index at diagnostic cut-off 3.60, which showed 81% sensitivity and 95% specificity with 0.945 AUC (P < 0.001). It was more sensitive to early lung cancer than to advanced lung cancer (sensitivity 87.5% vs 72.7%). Conclusion The ratios of CIC to CYFRA21-1 and PIC to p53 are useful biomarkers in lung cancer diagnosis and the combination of the ratios, LC index could be complementary tool for lung cancer screening with radiological tests.