Progression Criteria for Cancer Antigen 15.3 and Carcinoembryonic Antigen in Metastatic Breast Cancer Compared by Computer Simulation of

simulation models for performance comparisons of dif-ferent tumor marker assessment criteria to define pro-gression or nonprogression of metastatic breast cancer. Methods: Clinically relevant values for progressive can-cer antigen 15.3 and carcinoembryonic antigen concen-trations were combined with representative values for background variations in a computer simulation model. Fifteen criteria for assessment of longitudinal tumor marker data were obtained from the literature and computerized. Altogether, 7200 different patients, each based on 50 measurements, were simulated. With a sampling interval of 4 weeks, the monitoring period for each event was;3.8 years. Results: Modulation of the background variation, the starting concentrations, and the cutoffs enabled identi