Diagnostic and prognostic values of carcinoembryonic antigen in medullary carcinoma of the thyroid.

This study was conducted to compare the diagnostic and prognostic values of calcitonin (CT) and carcinoembryonic antigen (CEA) measurements in patients with medullary carcinoma of the thyroid (MCT). Plasma CEA, basal CT (BCT), and peak CT (PCT) levels after pentagastrin stimulation were determined in 15 patients with occult familial MCT before treatment. CEA was elevated in 11 patients (73%), BCT in 8 patients (53%), and PCT in all patients. The prognostic values of serial CEA and BCT determinations were studied in 24 other MCT patients followed for a period of 1.5-8 yr. These patients were divided into 2 groups; group I consisted of 11 patients with normal serial CEA levels, and group II consisted of 13 patients with persistently elevated CEA levels. In group I, 2 patients (18%) developed metastases compared with 10 patients (77%) in group II (P less than 0.001). Elevated BCT levels were found in all patients with metastases as well as in 63% of patients with no evidence of disease. When CEA time curves were studied, three patterns could be identified: 1) a steep slope with rapidly rising CEA levels in patients with rapidly progressive disease, 2) a flat slope in patients with no metastasis or nonprogressive disease, and 3) an intermediate type of slope in patients with slowly progressive disease. Slope analysis of BCT time curves was not done because of marked fluctuations in BCT levels. PCT after pentagastrin stimulation remains the best diagnostic marker for MCT. However, CEA may be a better prognostic indicator, as it discriminated more efficiently between patients with and without metastasis. Slope analysis of CEA time curve and calculation of the doubling time are recommended, as they correlated well with the course of the disease.