Prospective Study into the Incidence of Lambert Eaton Myasthenic Syndrome in Small Cell Lung Cancer

IntroductionThe Lambert Eaton myasthenic syndrome (LEMS) is a paraneoplastic disorder associated with raised serum voltage-gated calcium channel (VGCC) antibodies in patients with small cell lung cancer (SCLC). VGCC can also be found in patients with SCLC and cerebellar ataxia. This was a prospective study to assess the incidence of clinical and subclinical LEMS or other neurologic disease in patients with SCLC.Patients and MethodsSixty-three unselected patients with cytologically or histologically confirmed SCLC consented to participate. Pretreatment assessment included a neurologic symptom questionnaire, examination for physical signs of LEMS or ataxia, measurement of serum titers of antibodies to P/Q-type VGCCs by radioimmunoassay in all patients and electrophysiological examination where appropriate.ResultsNeurologic symptoms unrelated to LEMS occurred in 26% of patients. Five patients (8%) had raised serum VGCC antibodies (range, 69–1553 pM/l) diagnostic of LEMS, two (3%) of whom had LEMS on clinical and electrophysiological grounds. Both also had mild cerebellar ataxia. There was no association between serum VGCC antibody titer and survival.ConclusionRoutine measurement of VGCC antibodies in patients without clinical LEMS is unlikely to assist either in management of SCLC or in assessment of prognosis.