[Long-term survival case of small-cell lung cancer with Lambert-Eaton myasthenic syndrome without anticancer therapy].

A 78-year-old man with complaints of appetite loss and weight loss visited our hospital in November 2006. Positron-emission tomography and computed tomography (PET/CT) showed swollen lymph nodes in the abdominal para-aorta, mediastinum and neck, with intense FDG accumulation. The pathological findings of the cervical lymph nodes revealed small-cell cancer. We diagnosed extensive small-cell lung cancer (SCLC), which occurred primarily in the left upper lobe. As subsequent CT revealed spontaneous shrinkage of the pulmonary nodule and swollen lymph nodes, the clinical course was monitored without anticancer therapy. In February 2007, progressive muscle weakness of the lower extremities developed. In July he was admitted with respiratory failure and required mechanical ventilation. Although we did not administer anticancer therapy due to his poor performance status, he survived for 30 months receiving mechanical ventilation, and the tumors continued to grow moderately. We diagnosed Lambert-Eaton myasthenic syndrome (LEMS) based on the clinical symptoms, the presence of anti-VGCC antibodies and waxing phenomenon on electromyography obtained in April 2009. Chemotherapy with amrubicin shrank the tumors, but his muscle weakness did not improve. Previous reports showed that a prognosis of SCLC with LEMS was better than that without LEMS. In this case, the tumors showed spontaneous regression without any anticancer therapy, and then increased moderately. The immune response was considered to have affected tumor growth.