SERUM NEURON-SPECIFIC ENOLASE AND IMMUNOHISTOCHEMICAL MARKERS OF NEUROENDOCRINE DIFFERENTIATION IN LUNG-CANCER

An enzyme immunoassay for serum neuron-specific enolase (NSE) was eval uated with respect to analytical performance and clinical utility and compared with immunohistochemical evaluation of neuroendocrine differe ntiation. Values obtained agreed well with values obtained using a rad ioimmunoassay method giving a correlation coefficient of 0.934. Analyt ical performance of the enzyme immunoassay was good but the diagnostic sensitivity of 82% in extensive and 67% in limited disease was insuff icient for serum NSE to be of value in the diagnosis of small cell lun g cancer (SCLC). Serum NSE decreased significantly in 11 of 15 patient s with SCLC following institution of chemotherapy. Classification of l ung cancers into SCLC and non small cell lung cancer (NSCLC) types is largely based on tumour morphology. Neuroendocrine differentiation may not be morphologically evident. Immunohistochemical staining of tumou r tissue with markers of neuroendocrine differentiation, i.e. NSE (bot h monoclonal and polyclonal antibodies) Leu 7, Chromogranin A and P G P 9.5 was performed in both patients with SCLC and NSCLC. 38 per cent of patients with NSCLC had both raised serum NSE and positive NSE (pol yclonal) immunoperoxidase staining of lung tissue. A further 35 per ce nt of patients showed a raised serum NSE or positive immunohistochemis try but not both. The presence of two positive immunoperoxidase marker s in lung tissue has been suggested as an indicator of responsiveness to chemotherapy in NSCLC patients. A number of factors may affect immu nohistochemical positivity in tissue sections and the additional use o f a serum marker may better define chemotherapy responsive groups.