Relation between Carcinoembryonic Antigen Levels in Colon Cancer Tissue and Serum Carcinoembryonic Antigen Levels at Initial Surgery and Recurrence.

OBJECTIVES Carcinoembryonic antigen (CEA) is widely used for postoperative surveillance of colon cancer. Even if serum CEA is negative at initial surgery, it may turn positive at recurrence. We investigated the relation between serum CEA levels and the immunohistochemical staining status of CEA in the primary and resected metastatic tissues. METHODS Out of 224 patients with recurrent colon cancer between 1998 and 2012, we studied 46 patients in whom serum CEA levels were measured and immunohistochemical staining for CEA was possible in the primary and metastatic tissues. RESULTS The positive rate of serum CEA did not differ between initial surgery and recurrence, regardless of whether the cutoff value was set at 5 or 10 ng/ml (p = 0.829, p = 0.671). There was no relation between the CEA staining status and serum CEA level at initial surgery. However, the CEA staining status of metastatic tissue was significantly related to the serum CEA level at recurrence (p = 0.0046 and p = 0.0026). CONCLUSIONS The immunohistochemical staining status of CEA in metastatic tissue is closely related to the serum CEA level. This finding suggests that serum CEA levels are influenced not only by the CEA production capacity of cancer cells but also by the ability of the surrounding tissue to release CEA into the blood.