Diagnostic impact of high serum midkine level in patients with gastric cancer

AIM: We evaluated the diagnostic impact of serum midkine (s‐MK) levels in patients with gastric cancer using a monoclonal antibody enzyme‐linked immunosorbent assay system (ELISA) to detect s‐MK levels. METHODS: Serum samples were obtained from 131 patients with gastric cancer including stage I (n = 71), stage II (n = 28), stage III (n = 16), and stage IV (n = 16) before surgery. Serum samples were analyzed using ELISA to detect soluble midkine. A cut‐off value was fixed at 421 pg/mL, and the sample divided into two groups: a high s‐MK group and a low s‐MK group. Clinicopathological factors and prognosis were compared between these two groups using univariate and multivariate analyses. Comparison of two groups was analyzed by Fisher's exact probability test. Statistical significance was considered at P < 0.05. RESULTS: High s‐MK was significantly associated with high carcinoembryonic antigen (CEA) (P < 0.01). Positive rate of s‐MK was higher than the positive rates of CEA in patients with stage I/II gastric cancer. Combination with CEA + CA19‐9 + s‐MK increased the positive rates of patients with stage I/II gastric cancer. No other clinicopathological factors were associated with s‐MK. Although the high s‐MK group showed worse overall survival than the low s‐MK group, the difference was not statistically significant. CONCLUSION: s‐MK level is increased even during early‐stage gastric cancer. Combined with s‐MK, the positive rate of CEA + CA19‐9 was increased in patients with stage I/II gastric cancer.