VARIABILITY OF TUMOR-MARKERS IN THE FOLLOW-UP OF PATIENTS RADICALLY RESECTED FOR BREAST-CANCER

The biological and analytical components of variability of tumor marke rs should be distinguished from the variations due to tumor progressio n. The aim of the present study was to evaluate tumor marker variabili ty in the follow-up of patients resected for breast cancer. So far, we have carried out 2,085 CEA and 2,550 CA 15-3 determinations in 435 pa tients. The total variability of both CEA and CA 15-3 was widely scatt ered among different subjects (CEA coefficient of variation 0-105%; CA 15-3 coefficient of variation 0-89.2%). The biological variability of CA 15-3, which was calculated in a limited number of cases, was scatt ered between 0 and 23% and was higher than the intra-assay variability . From these findings we conclude that when evaluating serial marker a ssays the intra-individual variability should be assayed initially to obtain a reference value of individual variability in relapse-free con ditions.