What is the approach to cancer workup and treatment in Lambert-Eaton myasthenic syndrome (LEMS)?

Updated: May 23, 2019
  • Author: David E Stickler, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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In patients with cancer, LEMS is usually not the major therapeutic concern: the primary concern is the cancer. Accordingly, when the diagnosis of LEMS is confirmed, perform an extensive search for an underlying malignancy with radiography and computed tomography (CT) of the chest, bronchoscopy, and possibly positron emission tomography (PET) scanning.

If no tumor is found, periodically search again for occult malignancy. Frequency of these evaluations is determined by the patient’s risk of cancer.

Patients younger than 50 years without history of long-term smoking have a low risk of associated malignancy, especially if evidence of coexisting autoimmune disease is present. Extensive surveillance for cancer may not be necessary for such patients. Patients older than 50 years with a history of long-term smoking almost certainly have underlying SCLC.

Initial treatment should be aimed at the neoplasm because weakness frequently improves with effective cancer therapy. No further LEMS treatment may be necessary in some patients.

Immunotherapy of LEMS without effective treatment of the underlying cancer usually produces little or no improvement in strength. A theoretical concern is that the immunosuppression may reduce immunologic suppression of tumor growth.

In patients with LEMS who do not have cancer, aggressive immunotherapy should be considered (see Pharmacologic Therapy and Plasma Exchange).

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