Catalase and superoxide dismutase activity were lower in the gastric cancer group (3.82 vs. 0.91; p ≤ 0.001 and 1.04 vs. 0.6; p ≤ 0.001) compared to their first-degree relatives (Tables 4 and 5), but no difference was observed in comparison with the control group. Here, CAT is linked to gastric cancer.