Carcinoembryonic antigen in patients with colorectal cancer: correlation between stage of disease and antigen level.

Carcinoembryonic antigen (CEA) levels were measured by radio-immunoassay in the sera of 339 patients with various stages of colorectal cancer. Of 298 patients considered to be free of disease, 61 (20.5%) were found to have elevated CEA values of greater than 10 ng/ml. Of these patients, 36 had subsequent disease progression, 23 had only a transient rise in CEA and 2 showed a persistent increase with no clinical deterioration during the study period. Of 41 patients with known active disease, only 27 (65.9%) had elevated CEA values, most greater than 30 ng/ml, whereas the remaining 14 patients had CEA levels less than 10 ng/ml. Of a total of 77 patients with known active colorectal cancer throughout the whole study period, these 14 (18%) represent the number of false-negative CEA determinations. This relatively high rate of false-negative measurements should not obscure the fact that full accordance between CEA levels and clinical status as determined throughout 38 months of follow-up, occurred in 323 of the 339 patients.