Elevated serum levels of fetal antigen 1,a member of the epidermal growth factor 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 non-small cell lung cancer (NSCLC) and compared to the normal reference interval (n = 177). Serum FA1 levels were significantly elevated 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 cutoff level the sensitivity for SCLC was 43% and the specificity 96%. There was 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 in normal serum/amniotic fluid with respect to size distribution and also revealed a reaction of immunological identity with FA1 in amniotic fluid.