Elevated serum levels of fetal antigen 1, a member of the epidermal growthfactor superfamily, in patients with small cell lung cancer

Serum levels of fetal antigen 1 (FA1) were quantified pretherapeutically in 16 patients with pneumonia, 30 patients with small cell lung cancer (SCLC) and 10 patients with nonsmall cell lung cancer (NSCLC) and compared to the normal reference interval (n = 177), Serum FA1 levels were significantly e levated in SCLC (p < 0.0001) but not in pneumonia or NSCLC (p = 0.1467 and p = 0.3262, respectively). With the 95th centile of the normal range as cut off level the sensitivity for SCLC was 43% and the specificity 96%. There w as no correlation to neuron-specific enolase levels or to the diagnosis of limited/extensive disease. Immunohistochemical analysis of a biopsy from 1 SCLC patient with an elevated serum FA1 also showed the presence of FA1 in tumor cells. FA1 in serum from SCLC patients was identical to that of FA1 i n normal serum/amniotic fluid with respect to size distribution and also re vealed a reaction of immunological identity with FA1 in amniotic fluid.