NCMP-38. To Treat or Not To Treat - Immune Checkpoint Inhibition in Patients with SCLC-associated LEMS

Abstract OBJECTIVE To describe neurologic outcomes in patients with Lambert Eaton Myasthenic Syndrome (LEMS) treated with immune checkpoint inhibition (ICI). INTRODUCTION Patients treated with ICI are at higher risk of developing or exacerbating underlying paraneoplastic neurological syndromes (PNS) (PMID: 38198120) (PMID: 36527972). LEMS, a PNS associated with small-cell lung cancer (SCLC), occurs when autoantibodies targeting calcium channels in pre-synaptic nerve terminals leads to neuromuscular junction disorder. First-line treatment of extensive-stage (ES)-SCLC, a highly aggressive malignancy, include ICI, platinum and etoposide (PMID: 30280641). PURPOSE Multi-center series of SCLC and LEMS patients on ICI. METHODS Case series of two patients with SCLC-associated LEMS treated with cancer immunotherapy. RESULTS Case 1: 55-year-old male presented with proximal weakness and diplopia prior to diagnosis of ES-SCLC. He was started on carboplatin, etoposide, and atezolizumab after which his weakness and diplopia worsened. Neuro-axis imaging without evidence of central or peripheral nervous system malignant involvement. She had positive VGCC antibodies (129.5 pmol/L). Patient started amifampridine, and experienced improvement in his LEMS symptoms. Patient continues atezolizumab maintenance treatment and amifampridine and remain LEMS symptom-free and there is no evidence of SCLC 2 years after diagnosis. Case 2: 55-year-old female who presented with bilateral proximal lower extremity weakness, autonomic dysfunction and weight loss was diagnosed with LEMS (positive VGCC antibodies) and ES-SCLC. She was started on amifampridine and prednisone for LEMS and carboplatin/etoposide for SCLC resulting in cancer remission. One year later, she was found to have brain metastasis treated with stereotactic radiosurgery and durvalumab. She subsequently experienced worsening of LEMS symptoms. Prednisone and amifampridine were increased and the ICI was discontinued. She had improvement in neurological symptoms without evidence of recurrent SCLC 3 years later. CONCLUSION Additional data is needed to better understand the safety of ICI in SCLC-associated LEMS.