# Circulating IgG Fragments for Gastric Cancer and Esophageal Cancer

## TL;DR

This study shows that IgG-LysK levels in blood can help detect early-stage gastric and esophageal cancers, especially when combined with other markers.

## Contribution

The study identifies IgG-LysK as a potential early detection biomarker for gastric and esophageal cancers.

## Key findings

- IgG-LysK levels were higher in cancer patients compared to healthy donors.
- False negatives were linked to advanced cancer stages and altered blood homeostasis markers.
- IgG-LysK combined with other markers could improve early cancer detection.

## Abstract

Blood serum of patients with gastric (n = 68) and esophageal (n = 43) cancer was assessed for proteolytic fragments of IgG. Serum samples of 20 healthy donors were used as a control. We analyzed indicators of hemostasis (prothrombin time, fibrinogen, plasminogen activity, a2-antiplasmin activity, protein C activity) in blood plasma and the level of total IgG in the blood serum. The median IgG-LysK of healthy donors was lower than in esophageal cancer and in patients with gastric cancer. ROC-analysis showed high sensitivity (91%) and specificity (85%) in the group with esophageal cancer but 68% and 85%, respectively, in patients with gastric cancer. Analysis of false negatives IgG-LysK in cancer patients showed that most patients had an advanced stage of cancer accompanied by metastases. Total IgG in the plasma of patients with false-negative IgG-LysK values was 30% lower than in samples with positive values, while the level of a2-antiplasmin was increased and the prothrombin time was shorter. These changes in blood homeostasis may be the reason for an increase in the proportion of false-negative values of the IgG-LysK coefficient. Circulatory IgG-LysK levels increase in the early stages of such cancers as gastric and esophageal cancers. Thus, when used in a panel with other more specific markers for these pathologies, this indicator can significantly increase the early detection of cancer.