title: Criteria for monitoring carcinoembryonic antigen: variability of sequential assays at elevated levels.
abstract: Fifty-five patients with advanced cancer and elevated plasma carcinoembryonic antigen (CEA) levels greater than 20 ng/mL (Roche assay) were monitored by clinical parameters for disease activity and a daily plasma specimen was obtained and stored frozen. In 45 patients with evaluable metastatic lesions, 35 were stable; five had progressive disease; and five had regressive disease. Plasma CEA in patients with stable disease showed an overall coefficient of variation of 13%. The CV did not differ according to various quantitative CEA levels from less than 100 ng/mL to greater than 1,000 ng/mL. The coefficient of variation in responding and progressive disease patients ranged from 13% to 63%. An analysis of CEA variability relative to the baseline CEA level was possible using the formula square root 2 times the variability about the mean; this yields a value of +/- 36% representing the range within which approximately 95% of sequential CEA levels would lie in the absence of a clinical change in disease. In 225 CEA determinations in stable disease patients, 6% demonstrated an increase beyond this level (36%) and none demonstrated a decrease of 36% or more from the baseline level. This study establishes guidelines for the boundaries of change in plasma CEA that may be applied as a criterion (in conjunction with standard objective disease parameters) for determination of tumor response to therapy.
mesh_terms: D000704:Analysis of Variance; D002272:Carcinoembryonic Antigen / Q000032:analysis*; D003110:Colonic Neoplasms / Q000097:blood / Q000276:immunology; D006801:Humans; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000097:blood / Q000276:immunology*; D011863:Radioimmunoassay; D012016:Reference Values; D013997:Time Factors
chemical_list: D002272:Carcinoembryonic Antigen