Dr Shah on Current Guidelines for Diagnosing Cancer-Associated LEMS

"The biggest things [to keep in mind when diagnosing LEMS] are recognizing the proximal weakness and the autonomic dysfunction from a diagnostic perspective.”

Shailee S. Shah, MD, a clinical assistant professor of neurology (MS/neuroimmunology) at Northwestern University Feinberg School of Medicine, expands on the most important factors to consider when diagnosing cancer-associated Lambert-Eaton myasthenic syndrome (LEMS), as per the updated National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Small Cell Lung Cancer (SCLC).

In August 2025, the NCCN updated its guidelines for the treatment of patients with SCLC to include new information on how to diagnose LEMS and a revision of symptom specificity. LEMS is specifically defined by the presence of proximal muscle weakness and autonomic dysfunction. Shah emphasized that recognizing these two key symptoms is one of the biggest initial steps in the diagnostic process.

The updated guidelines recommend that diagnosis should involve a neurological evaluation, ideally in consultation with a neurologist. Diagnostic testing may include specific auto-antibody testing for LEMS, particularly the PQ-type calcium channel antibodies. Although N-type voltage-gated calcium channel antibodies may also be tested, Shah noted that they may be less specific. The presence of specific antibodies can therefore be an indicator of LEMS, but careful interpretation is necessary when relying on those tests in isolation, Shah emphasized.

Finally, the guidelines also recommend the use of amifampridine as a potential treatment option in consultation with a neurologist. Engaging a neurologist is also recommended if there is high suspicion of LEMS, and electrodiagnostic studies, such as a nerve conduction study, should be considered, Shah advised.

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Shailee S. Shah, MD, details current screening and diagnostic guidelines for small cell lung cancer–associated LEMS.


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In today’s episode, we had the pleasure of speaking with Jacob Sands, MD, and Shailee Shah, MD, about considerations for diagnosing and managing Lambert-Eaton myasthenic syndrome (LEMS), particularly in the context of small cell lung cancer (SCLC). Dr Sands is associate chief of the Lowe Center for Thoracic Oncology and the Oncology Medical Director of the International Patient Center at Dana-Farber Cancer Institute, as well as an assistant professor at Harvard Medical School in Boston, Massachusetts. Dr Shah is a clinical assistant professor of neurology (MS/neuroimmunology) at the Northwestern University Feinberg School of Medicine in Chicago, Illinois. 

In our exclusive interview, Drs Sands and Shah discussed LEMS symptom identification, the importance of paraneoplastic panels for assessing neurologic dysfunction in patients with SCLC, the need for specific autoantibody testing, and what guidelines currently note as best practices for the diagnosis of this disease. 

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Drs Sands and Shah discuss LEMS symptom identification and what guidelines currently note as best practices for the diagnosis of this disease. 

Accurate Symptom Identification and Guidelines Support LEMS Screening and Diagnosis: With Jacob Sands, MD; and Shailee Shah, MD

Dr Leal on Clinical Considerations Surrounding the Diagnosis of LEMS in Patients With Lung Cancer

“As a medical oncologist, seeing patients with SCLC or [potentially] NSCLC, the critical thing is to think about the clinical presentation of LEMS. There needs to be awareness and education on the symptoms, because sometimes the symptoms can be vague at initial onset, and that can delay diagnosis or [lead to] misdiagnosis, especially in somebody with SCLC who may already have deconditioning.”

Ticiana Leal, MD, a professor and director of the Thoracic Medical Oncology Program in the Department of Hematology and Medical Oncology at Emory University School of Medicine, as well as medical director of the Clinical Trials Office at Winship Cancer Institute, outlined key considerations for medical oncologists in recognizing and diagnosing Lambert-Eaton myasthenic syndrome (LEMS), particularly in the context of small cell lung cancer (SCLC) and, in rarer cases, non–small cell lung cancer (NSCLC).

She emphasized that timely identification of LEMS is critical, as early symptoms may be subtle and easily attributed to cancer-related deconditioning or treatment effects, leading to missed or delayed diagnosis. Leal underscored the need for oncologists to maintain a high index of suspicion when evaluating patients with neuromuscular symptoms. 

LEMS often presents with a clinical triad consisting of proximal muscle weakness, dysautonomia, and areflexia or hyporeflexia. Proximal weakness, particularly when out of proportion to the patient’s disease burden or functional status, should prompt consideration of LEMS. Leal stressed that some symptoms may be mistakenly attributed to systemic illness or chemotherapy-related fatigue, highlighting the importance of clinician awareness.

Once LEMS is suspected, a thorough neurologic examination is essential, followed by confirmatory diagnostic testing. Leal explained the importance of ordering voltage-gated calcium channel (VGCC) antibody testing, which is highly specific for LEMS and can confirm the diagnosis in the majority of cases. She noted that VGCC testing should be pursued promptly whenever clinical suspicion arises.

Ticiana Leal, MD, discusses clinical considerations surrounding the diagnosis of LEMS in patients with lung cancer. 

Managing LEMS in SCLC and Oncology Care | Supplements and Featured Publications

Dr Shah on Current Guidelines for Diagnosing Cancer-Associated LEMS

Accurate Symptom Identification and Guidelines Support LEMS Screening and Diagnosis: With Jacob Sands, MD; and Shailee Shah, MD

Dr Leal on Clinical Considerations Surrounding the Diagnosis of LEMS in Patients With Lung Cancer