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Abstract
The long-term intra-individual variation of the title tumour markers was studied in the group of 33 patients which developed no relapse. The average biological intra-individual CV was 11.2% for CA 15—3 and 14.9% for MCA whereas those of CEA strongly depended on the concentration. The intra-individual standard deviation of CEA was independent of concentration and amounted to 0.23 g/L. Individual reference ranges the analytes were much smaller than the group reference ranges. Individual reference limits were calculated on the basis of the average intra-individual variation. In 21 of the 22 patients who developed recurrence during the follow-up period, individual reference limits of CA 15—3 and/or CEA were exceeded 1 to 31 months (median 10 months) before clinical evidence (diagnostic sensitivity 95%). Group reference limits were exceeded only in 13 patients (diagnostic sensitivity 60%) and occurring later. The diagnostic specificity was 97%. MCA did not provide additional information. The combination of CA 15—3 and CEA is an excellent for detection and exclusion of recurrence in the follow-up of breast cancer patients if decision-making is based on individual reference limits. Improvement of the long-term analytical quality of the tumour marker assays, particularly in the low concentration range is necessary.