Carcinoembryonic antigen in monitoring of response to cetuximab plus FOLFIRI or FOLFOX-4 in patients with metastatic colorectal cancer.

First-line treatment of metastatic colorectal cancer with combinations of cetuximab and irinotecan-based or oxaliplatin-based chemotherapy has shown promising efficacy. The clinical response to such treatment is generally assessed by tumor measurement through imaging. This study was performed to evaluate the correlation between serial changes in imaging results and carcinoembryonic antigen (CEA) levels. In 64 patients with metastatic colorectal cancer receiving cetuximab plus FOLFIRI or FOLFOX-4 chemotherapy we retrospectively analyzed the relationship between changes in serum CEA and changes in imaging results throughout the treatment course. Response in terms of serum CEA change was defined as a ≥50% drop in CEA level for more than 4 weeks. The sensitivity and specificity of serum CEA changes after targeted chemotherapy in relation to imaging results were 80.5% (33/41) and 73.9% (17/23), respectively, with a diagnostic accuracy of 78.1 % (50/64). The progression-free survival time of responders assessed by serum CEA change was significantly longer than that of nonresponders (p=0.0091). Our results highlight the importance of serum CEA monitoring in assessing the response to targeted chemotherapy and in predicting the prognosis of patients with metastatic colorectal cancer.