Tumor Markers CEA, CA19-9 and CA125 in Monitoring of Response to Systemic Chemotherapy in Patients with Advanced Gastric Cancer

Background: To evaluate whether tumor markers can be used to assess response to systemic chemotherapy, we analyzed preliminarily the relationship between the response to chemotherapy based on serial imaging and on change in serum tumor marker level of CEA, CM 9-9 and CM 25. Methods: We analyzed 26 patients with advanced gastric cancer in whom at least one of the tumor markers CEA, CA19-9 and CA125 was elevated before systemic chemotherapy with regard to the relationship between the change in serum tumor marker level and response assessment by imaging studies throughout the treatment course. A responder was defined as showing a ≥50% drop in tumor marker level for more than 4 weeks. Results: The sensitivity and negative predictive value of falling tumor marker level after chemotherapy for a partial response in imaging was 100%. When patients were categorized as responders or non-responders, a significant correlation was observed between the assessment of response by tumor markers and by imaging studies. The survival time of responders assessed by tumor markers was significantly longer than that of non-responders. Conclusions: The measurement of tumor markers might be useful in monitoring response and in predicting the prognosis of patients with advanced gastric cancer treated with systemic chemotherapy. Tumor markers may be used as a means of monitoring treatment in patients when in an imaging study it is difficult to assess response to chemotherapy in clinical practice. Further studies are required to confirm these findings.