CA LEMS in Small Cell Lung Cancer: Disease Overview and the Case for Earlier Recognition

Dr. Misty Shields introduces the program on cancer-associated Lambert-Eaton myasthenic syndrome (CA LEMS) and its association with small cell lung cancer (SCLC), joined by Dr. Ditte Primdahl and Dr. Triparna Sen. CA LEMS is a paraneoplastic neuromuscular junction disorder characterized by proximal muscle weakness, hyporeflexia, and autonomic dysfunction. It arises when autoantibodies directed against presynaptic voltage-gated calcium channels (VGCCs) impair acetylcholine release at the neuromuscular junction. Approximately 50% to 60% of CA LEMS cases are paraneoplastic in origin, with SCLC accounting for the vast majority. In the oncology setting, CA LEMS may predate the SCLC diagnosis by months to years, emerge during treatment, or be misattributed entirely to cancer-related fatigue, chemotherapy toxicity, or other treatment-related adverse events. The diagnostic odyssey for many patients is prolonged, and the window for meaningful intervention is narrow.

Dr. Primdahl frames CA LEMS from a neuromuscular standpoint as diagnostically satisfying when identified (the clinical triad, electrodiagnostic pattern, and serologic marker align in a way few other neuromuscular disorders do), but emphasizes that a large proportion of patients with CA LEMS are never referred for neurologic evaluation, with the diagnosis made late or not at all. Today's goal is to think across specialties about how to change that.

Dr. Sen frames the oncologic challenge: the overlap between CA LEMS symptoms and the everyday symptom burden of SCLC, including fatigue, weakness, functional decline, makes it genuinely difficult to separate signal from noise. The goal is to give oncologists the tools to recognize when that signal is present and act on it without delay, because early recognition can genuinely change the trajectory for patients with CA LEMS.