CA-62: A new biomarker for the detection of early-stage renal cell carcinoma.

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Background: The American Cancer Society classifies Renal Cell Carcinoma (RCC) to be among the ten most common cancers. However, in spite of this need, effective biomarkers for early-stage detection of RCC are not yet available. The purpose of this study was to assess the diagnostic characteristics of a carcinoma-specific transmembrane N-glycoprotein biomarker, CA-62, for the detection of early-stage kidney cancer. Blinded serum samples from 204 patients were included in the clinical study, of which 68 had TNM-classified stages IA, IB, IIA or IIB renal cell carcinomas, while 136 were drawn from healthy volunteers. Methods: Quantitative measurement of serum CA-62 levels was performed using a chemiluminescent immunoassay ("JVS Diagnostics" LLC). Statistical analysis (MedCalc; version 19.7.4, MedCalc Software Ltd, Belgium, EU) was used to assess the diagnostic characteristics of the CA-62 biomarker for detection of RCC, including sensitivity and specificity, and test accuracy. Results: Significantly higher median concentrations of CA-62 were found in sera of RCC patients compared to those found in healthy controls as follows; stage I A, B (8,935 U/mL), stage II A (6,291 U/mL), stage II B (8,808 U/mL), and healthy controls (2,815 U/mL). It was expected that serum CA-62 levels would be elevated at these early stages of RCC (Stages I-IIB), demonstrating significant overexpression of this epithelial carcinoma marker during the initial stages of cancerogenesis. The results of the study are presented in the table. Area under the ROC curve (AUC) for RCC patients vs. healthy controls was 0.98 with a 95% CI (0.950-0.994), z-statistics (67.3), and a significance of p<0.0001. Conclusions: CA-62 demonstrated a 94.3% sensitivity for RCC at 96% specificity during the early stages of kidney cancer. Given that CA-62 is not specific for kidney cancer, it is reasonable to suggest that use of a combination of CA-62 with some other biomarkers that may lack the sensitivity of CA-62 but are often elevated in renal cell carcinoma patients, such as tumor-infiltrating lymphocytes and/or possibly some inflammation biomarkers. In particular, the combination of transmembrane glycoproteins CA-62 and CD105, combined with biomarkers such as Endothelial Vascular Growth Factor (EVGF) and/or a growth factor derived from platelets (PDGF) could be successfully used for kidney cancer screening in order to achieve both high sensitivity and specificity for RCC detection.[Table: see text]