Serum neuron-specific enolase as a tumor marker in the diagnosis and follow-up of small-cell lung cancer.

Serum samples for the determination of neuron-specific enolase (NSE) levels were collected at diagnosis, after induction of chemotherapy and at relapse in order to assess the value of NSE in the diagnosis and management of small-cell lung cancer (SCLC). At diagnosis, 47 of 64 patients with SCLC (73%) had abnormal NSE values (i.e. NSE > 12.5 micrograms/l). Mean NSE values were significantly higher in patients with extensive disease compared to limited disease. Patients with other malignancies or benign lung diseases presented with elevated NSE levels in approximately 15 and 4% of cases. Sensitivity, specificity and predictive value of positive results of NSE at diagnosis were 74, 83 and 71%, respectively, for a cutoff value of 12.5 micrograms/l. In responders mean NSE dropped significantly from 46.1 micrograms/l before chemotherapy to 17.0 micrograms/l after three cycles of chemotherapy. Nonresponders as a group showed a nonsignificant drop. At relapse mean NSE increased from 6.5 micrograms/l at the time of response to 51.9 micrograms/l at the time of progression, but in 5 of the 18 evaluable patients normal levels persisted. Thus, evolution of NSE in patients receiving chemotherapy correlated well with tumor volume in patients who responded, but often failed to predict a therapeutic outcome in patients with apparently chemoresistant tumor (i.e. some nonresponders showed a decrease in NSE levels). A similar lack of correlation between NSE levels and tumor volume was seen at the time of relapse. We conclude that the determination of NSE levels is of doubtful utility in the diagnosis and follow-up of SCLC patients.