[Neuron-specific enolase (NSE) in the surveillance of small cell cancers. An evaluation of the prognostic information using Markov's model].

RATIONALE

An elevated serum NSE concentration is generally a bad prognostic sign when a diagnosis of small cell lung cancer is made. However, the marker may vary from time to time crossing the discriminant threshold (12.5 ng/ml) in one direction or the other. These variations are presumed to reflect the progress of the disease but it has not been shown that the risk of death from the disease is changed by alterations in the serum concentration of NSE. To resolve this question we have used Markov's mathematical model (homogeneous over time and in three states).

METHOD

A prospective study has included 52 patients suffering from small cell cancer and treated with chemotherapy based on cisplatin. The NSE was measured following each treatment and three monthly in subsequent follow up. Markov's model was studying the intensities of transition and the risks of death between the two following transient states: living with an NSE concentration of < or = to 12.5 ng/ml, living with an NSE concentration of > 12.5 ng/ml, and an absorbing state: death.

RESULTS

When a level of > 12.5 ng/ml was noted the mean time of maintaining in this state was short (123 days). During this time when a transfer was effected in 44 per cent of cases there is turn towards the opposite state (living with a concentration < 12.5 ng/ml) showing the real reversibility between the two transient states. When a patient had an elevated concentration of serum NSE the risk of death was 2.23 times greater than in the opposite state (living with a low NSE; P < 0.01).

CONCLUSION

The observation of an elevated NSE concentration at any time in the follow up of patients suffering from small cell cancer was strongly associated with an elevated risk of death but a return from this state towards a state of less risk (living with a low NSE level) remains possible. This works suggests that the NSE levels may be useful in the follow up of small cell lung cancer.