Long-term treatment and prognosis of LEMS depend on whether it occurs with or without cancer. Although cancer is life-threatening, it can be treated with radiation, surgery or chemotherapy. When these treatments are successful and the cancer goes into remission, LEMS usually goes into complete or partial remission as well.
Prior to cancer treatment, or in LEMS patients without cancer, immunosuppressant drugs, IVIg and/or plasmapheresis  often are helpful. More information about these treatments can be found on the Myasthenia Gravis Medical Management page .
Symptomatic relief can be achieved with Mestinon and/or 3,4-diaminopyridine (3,4-DAP), a drug that prolongs the opening of VGCC in nerve endings and thus enhances ACh release. This drug (3,4-DAP) may be hard to obtain, but you can ask about it through your MDA clinic  physician. It also may be available through research studies .
For more about Lambert-Eaton myasthenic syndrome management, see: Keeping Your Focus: Eye Care in Neuromuscular Disorders  and Not Always Smooth Sailing: Charting a corticosteroid course .