Diagnostic significance of CA-62 cancer antigen for early detection and differential diagnosis of non-small cell lung cancer: results of the blind clinical trials

Background. The combination of several diagnostic methods is used to predict treatment outcomes, assess overall survival, and increase the positive predictive value of detecting malignant lung and bronchial tumors.

Aim. To evaluate the diagnostic value of the CLIA-СА-62 chemiluminescence immunoassay reagent kit for the detection of early (Ia–IIb) and advanced (IIIa–c) stages of lung cancer (LC) in a double-blind clinical study and to assess the use of the CA-62 cancer antigen as a supportive decision-making tool in LC diagnosis in patients with suspicious changes on the tomogram or as a tool for pre-screening of LC prior to computed tomography (CT) to increase diagnostic sensitivity in the detection of early (I and II) stages of LC.

Materials and methods. A blinded clinical study was conducted on 304 clinically verified serum samples, including 141 samples from patients with non-small cell LC (NSCLC), 133 healthy volunteers, and 30 chronic obstructive pulmonary disease patients. Quantification of other well-known tumor markers used in the diagnosis of LC (CEA, CA-125, CA 15-3, CA 19-9, CYFRА 21-1, NSE, and SCC), as well as the CA-62 marker in all serum samples was performed using electrochemiluminescent immunoassay Elecsys CA-125, ELECSYS CA 19-9, ELECSYS CYFRА 21-1 and ELECSYS SCC (COBAS, Roche Diagnostics GmbH, Germany, EU), enzyme-linked immunoassay CA 15-3-ELISA-BEST, CEA-ELISA-BEST, NSE-ELISA-BEST (AO Vector-Best, Russia) and chemiluminescent immunoassay CLIA-СА-62 (JVS Diagnostics, Skolkovo, Moscow, Russia).

Results. CA-62 glycoprotein showed the highest level of expression at stage I NSCLC (12 745 U/mL) compared to other tumor markers studied and remained very high at the later stages of cancer: stage II (11 261 U/mL) and stage III (10 220 U/mL). A comparative analysis of the ROC curves of the most promising tumor markers CEA, CYFRA 21-1, SCC, and CA-62 for the entire NSCLC cohort versus all healthy volunteers and patients with chronic obstructive pulmonary disease showed a significant difference in the area under the curve between CA-62 (AUC 0.981) and other markers: CEA (AUC 0.84)> CYFRA 21-1 (AUC 0.753)>SCC (AUC 0.682). When detecting early stages (I and II) of NSCLC, a comparison of the sensitivity of the studied tumor markers showed the following pattern: CA-62 (92%)>CEA (37%)>CYFRA 21-1 (9%) and SCC (9%)>NSE (4.5%)>CA-125 (3%)>CA 15-3 (1.5%)>CA 19–9 (1%). In contrast to the CEA, CA 15-3, CA-125, NSE, CA 19-9, CYFRA 21-1, and SCC tumor markers, which are expressed proportionally to tumor growth, the epithelial carcinoma marker CA-62 showed the highest diagnostic indicators in the detection of LC early stages (I–II): sensitivity 92.5%, specificity 96.3%, positive predictive value 91.2%, NPV 97%, with 95% accuracy of LC detection with biopsy.

Conclusion. The study results showed that in order to increase the specificity of computed tomography in diagnosing LC in patients with suspicious lesion on the CT scan on the tomogram, the use of the carcinoma-specific marker CA-62 can improve the interpretation of the localized focus visualized and increase the accuracy of differential diagnosis at the early stages of LC to 96%, thus contributing to an increase of the overall survival among patients with lung cancer. Of the entire panel of markers, only glycoprotein CA-62 showed a strong correlation with histology (kappa 0.91) in identifying the malignant process with inconclusive results of low-dose CT (LDCT). In the future, introducing the CA-62 marker to the current system for assessing the LC risk as a pre-screening for LDCT can improve the detection of early LC by reducing false-positive results. Once introduced into existing screening programs, it can help significantly reduce the number of patients who need LDCT, decreasing the workload of LDCT and reducing radiation exposure.