Inability of serum neuron-specific enolase to predict disease extent in small cell lung cancer

Serum neuron-specific enolase (NSE) levels were measured before treatment in 112 patients diagnosed as having small cell lung cancer in our department. All these patients underwent exhaustive staging procedures: 53 had limited disease (LD) and 59 extensive disease (ED). Serum NSE was elevated in 83% of the patients (i.e. 71% of the patients with LD and 93% of the patients with ED). Mean values of NSE differed significantly according to disease extent. A receiver-operating characteristic curve was constructed with different cut-off levels of serum NSE in order to determine the accuracy of NSE for identifying ED. There was no level of NSE capable of predicting with sufficient accuracy the presence of ED. The best compromise was given by a threshold of 35 micrograms/l: 60% of the ED patients had a serum NSE above 35 micrograms/l but 30% of the LD patients also had a serum NSE above 35 micrograms/l.