Associations between serum CA724 and HER2 overexpression among stage II–III resectable gastric cancer patients: an observational study

OBJECTIVES: Associations between serum tumor biomarkers and human epidermal growth factor receptor 2 (HER2) overexpression among locally advanced gastric cancer patients were yet to be determined and therefore warranted investigation. RESULTS: A total of 318 patients were analyzed. The odds ratios of CA724 were 4.79 (95% CI 1.55–14.79) and 6.29 (1.40–28.19) in comparing the HER2 (2+/3+) and HER2 (3+) with the negative group, respectively (p < 0.05). A combination of the four biomarkers yielded slightly but not significantly greater areas under the curve (AUC = 0.83; 0.71–0.94) than that of serum CA724 alone (0.80; 0.68–0.91); however, an index generated from the combination had better diagnostic performance with 85.7% sensitivity, 80.4% specificity and 97.8% negative predictive value to predict the strong overexpression of HER2 (3+). CA199, CEA or CA125 alone was not associated with HER2 overexpression. Leave-one-out cross-validation found a consistent association between serum CA724 and HER2 (2+/3+) overexpression. METHODS: Patients undergoing radical gastrectomy from 8/2012 to 12/2013 and with pathological stage II–III gastric cancer were retrospectively analyzed. HER2 expression of the surgical samples was estimated using immunohistochemistry; serum CA724, CA199, CEA and CA125 were preoperatively tested. Internal validation was performed using the leave-one-out approach. CONCLUSIONS: Serum CA724 is significantly associated with the overexpression of HER2 among locally advanced gastric cancer patients. The combination of CA724, CA199, CEA and CA125 is better than serum CA724 alone in predicting HER2 overexpression. External validation and further investigation of the biological mechanisms of these associations are required.