TUMOR-MARKERS IN BREAST-CANCER FOLLOW-UP - A POTENTIALLY USEFUL PARAMETER STILL AWAITING DEFINITIVE ASSESSMENT

Background: Although tumor markers are frequently used in the follow-u p of patients with breast cancer, two points are still being debated: 1) their cost/effectiveness has been neither demonstrated nor disprove d 2) the reliability of the currently used dichotomous division into a positive/negative cut-off should be definitely validated. Dynamic cri teria of interpretation based on serial serum samples would probably b e more effective for early detection of relapse.Patients and methods: The aim of the present study was to compare the dichotomous cut-off ba sed decision criteria to a dynamic serial sample based assessment of t umor markers. Since 1989, 794 patients have been followed in 11 instit utions. CEA and CA15.3 were measured once a month for three months bef ore every clinical examination. The present paper concerns the evaluat ion variability in 405 patients without evidence of disease in the fir st three institutions joining the study. Results: In patients without evidence of disease, the coefficient of variation of all samples for e very patient showed a median value of 19 for CEA and 21 for CA15.3. Va riability was negatively associated with the antigen level and was mos t likely due to the analytical component. This was also confirmed by t he significant difference in variability among the three institutions evaluated. The median value of the critical difference was 53% for CEA and 57% for CA15.3. Conclusions: 1) Individually tailored dynamic dec ision criteria are applicable in about 50% of the cases. 2) The proble m of improving the precision of tumor marker assays in the low dose ra nge must be urgently addressed to the manufacturers of tumor markers b y the scientific community in order to apply individually tailored dec ision criteria for patients in whom the serum level of biological mark ers is low.