Assessment of CA 15.3, CEA and TPA concentrations during monitoring of breast cancer

The variability of the tumor markers cancer antigen (CA) 15.3, carcinoembry onic antigen (CEA) and tissue polypeptide antigen (TPA) during steady state concentrations and the rate of increase during progression is described. O ne hundred and ninety-two patients were monitored during first-line chemoth erapy for metastatic breast cancer and during follow-up. Blood specimens we re sampled approximately every four weeks. Steady state concentrations were registered for 77 (CA 15.3), 96 (CEA), and 127 (TPA) patients with below c utoff level values and for 28 (CA 15.3), 25 (CEA), and 11 (TPA) patients wi th above cutoff level values. Clinical and marker progression was registere d for 75 (CA 15.3), 62 (CEA), and 57 (TPA) patients. The coefficients of to tal variation of steady state concentrations (comprising the intra- and int erassay analytical imprecision and the within subject biological variation) were higher below (14.9% CA 15.3, 15.4% CEA, 25.9% TPA) than above cutoffs (9.6% CA 15.3, 6.0% CEA, '19.9% IPA). The variability was similar for CA 1 5.3 and CEA but higher for TPA. During progression the rates of increase in concentrations were similar for CA 15.3 (0.0257) and CEA (0.0214) and lowe r than for TPA (0.0346). Our data indicate that criteria for assessment of sequential tumor marker concentrations should consider the marker in questi on, the steady state variability, the cutoff value, and the rate of increas e during disease progression.