Radioimmunoassay of carcinoembryonic antigen and clinical significance of its level in plasma.

The level of carcinoembryonic antigen (CEA) in the plasma was measured in 258 patients, consisting of 198 patients with various cancers and 60 with various non-malignant diseases. As the normal control, the plasma CEA level was examined in 330 apparently healthy individuals and the value was 3.1 +/- 1.1 ng/ml on the average. If the level higher than 4.2 ng/ml could be assumed to be above the normal, 109 out of 198 (55%) patients with malignant diseases were considered to show abnormally elevated CEA values. Based on the above criterion, the CEA titer was abnormally elevated only in 11 out of 60 cases (18%) without cancers. Among cancerous patients, the ones with carcinomas of the digestive tract and the lung exhibited a positive titer of CEA higher than 10.1 ng/ml. When the relationship between the plasma CEA level and histological findings in patients with lung cancer was examined, cases with the adenocarcinoma had more elevated titers than those with any other types of lung cancer. It was also found, by the serial estimation of plasma CEA, that the titer dropped after a successful therapy but elevated again with the recurrence of cancer. Repeated estimation of Cea is thought to be valuable as an indicator for clinical phases of cancer patients.