Significance of serum neuron-specific enolase as a predictor of relapse of small cell lung cancer.

We conducted a prospective study to evaluate the significance of serum neuron-specific enolase (NSE) as a predictor of relapse of small cell lung cancer (SCLC). Patients entered into the study were drawn from those who had shown a complete or partial response to first-line chemotherapy with a concurrent decline in the NSE level to less than 10 ng/ml. When the serum NSE level increased to more than 15 ng/ml, the patient was restaged on the basis of clinical, radiological, and bronchoscopic examinations. During the period from August 1988 to December 1990, 57 patients with SCLC were enrolled and followed up until May 1992. Of these patients, 45 had clinical relapses, and 14 (31%) of them showed a clear elevation of the serum NSE level prior to the clinical recognition of relapse. Although one false-positive case was noted, this involved only a transient elevation of the NSE level. In patients who showed increased NSE levels, the relapses occurred in more difficult to detect silent sites such as the adrenal gland, liver, and deep lymph nodes. In addition, the percentage of patients demonstrating high NSE levels who were able to benefit from salvage chemotherapy was higher than for those who did not (RHO < 0.05). Our results indicate that serial NSE measurements are useful for the early prediction of SCLC relapse and should help to facilitate early administration of salvage chemotherapy for affected patients.