Immunoreactive carcinoembryonic antigen [CEA] levels in feces from colorectal cancer patients.

Immunoreactive CEA (IR-CEA) in feces or sera from 20 volunteers and 20 patients with colorectal cancer were measured before and at various intervals after surgery by a radioimmunoassay utilizing a "one step sandwich method." Elevated fecal IR-CEA level was observed in 17 of 20 patients with colorectal cancer; elevated serum CEA levels were observed in only 7 of all patients. There could not be found any correlation between fecal IR-CEA levels and Dukes' classification; there was but a little correlation between serum and fecal IR-CEA levels. In 8 of 14 patients treated by surgery, fecal IR-CEA levels obviously dropped, but in 2 patients with hepatic metastasis they were found rising in spite of colon tumor removal. It was speculated from these data that high values of fecal CEA depend on mass production of CEA by cancer cells. From these observations, it appears that fecal IR-CEA level presents a more ideal diagnostic competency in colorectal cancer than serum CEA level.