Lung cancer therapy triggers severe LEMS muscle weakness for man, 76
Treatment to restore muscle strength allowed patient to continue cancer care
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An elderly man with an aggressive form of lung cancer complicated by Lambert-Eaton myasthenic syndrome (LEMS) saw his autoimmune symptoms worsen — with more limb weakness and reduced reflexes — while receiving durvalumab, an immune-related cancer therapy, according to a new case report.
Appropriate treatment to restore his muscle strength allowed the man to continue cancer care, this time with chemotherapy, and ultimately achieve meaningful improvements in his physical function and quality of life, the researchers reported. A combination of LEMS therapies was used to ease the man’s symptoms and help his muscle strength return to normal, per the report.
“This case highlights the importance of early recognition and standardized management of paraneoplastic [cancer-associated] LEMS in enhancing functional recovery and enabling the safe continuation of antitumor therapy,” the researchers wrote.
The study, “Lambert-Eaton Myasthenic Syndrome During Immunotherapy in Extensive-Stage Small-Cell Lung Cancer: A Case Report,” was published in the British Journal of Hospital Medicine.
In most cases of LEMS, self-reacting antibodies mistakenly attack voltage-gated calcium channels (VGCCs), specific channel proteins found at the neuromuscular junction, which is the site where nerve cells communicate with muscles.
This disrupts the transmission of nerve signals to muscles, leading to LEMS symptoms such as muscle weakness, poor tendon reflexes, swallowing issues, and problems in the autonomic nervous system. That system controls involuntary functions such as heart rate and blood pressure.
Half of LEMS cases occur in people with lung cancer
The autoimmune disorder is frequently associated with an underlying cancer, with about 50% to 60% of LEMS cases occurring in people with small cell lung cancer (SCLC), an aggressive form of lung cancer.
This is because some cancer cells also carry VGCCs on their surface, and antibodies produced against the tumor may also mistakenly target VGCCs at the neuromuscular junction, triggering LEMS. In such cases, treating the underlying tumor is the first-line treatment for LEMS.
Immune checkpoint inhibitors (ICIs), such as durvalumab (sold under the brand name Imfinzi), are a type of immune-related therapy, or immunotherapy, that has become a standard treatment for SCLC.
These therapies boost the immune system’s ability to recognize and attack cancer cells. However, activating the immune system can cause unwanted immune-mediated complications, and recent evidence suggests ICIs may also trigger or worsen LEMS, according to the scientists.
“Therefore, early recognition, accurate diagnosis, and standardized management of [immune-mediated adverse events] are critical during immune checkpoint inhibitor (ICI) therapy,” the researchers wrote.
Here, three researchers in China described the case of a 76-year-old man with extensive-stage SCLC, meaning the cancer had spread to other parts of the body. His LEMS symptoms worsened while receiving maintenance treatment with durvalumab.
The man, who had a 10-year history of high blood pressure and chronic kidney disease, first sought medical attention in July 2024 because of progressive weakness in his arms and legs. Imaging scans revealed a tumor in his lung, and subsequent testing confirmed a diagnosis of SCLC.
Electromyography, a test that measures electrical activity in nerves and muscles, showed characteristic abnormalities seen in LEMS, leading doctors to diagnose the autoimmune disorder.
The man was treated with a standard combination chemotherapy (etoposide and carboplatin) followed by maintenance treatment with durvalumab, after which his muscle strength improved. This suggested that both the cancer and LEMS were responding to therapy.
However, in February 2025, while still on durvalumab, he was admitted to the hospital due to a six-month history of generalized muscle weakness that had worsened in the previous week. He had also developed immune-related diabetes, a known complication of ICI therapy, the researchers noted.
Early recognition of complications key during cancer therapy
Doctors then treated him with intravenous immunoglobulin (IVIG), an antibody-based therapy that helps prevent LEMS-causing autoimmune attacks. He was also given pyridostigmine (sold in the U.S. as Mestinon), a medication approved for myasthenia gravis, a related condition, that is also used off-label to treat muscle weakness in LEMS. The treatment led to rapid neurological improvement, with his muscle strength returning to normal, according to the researchers.
Further scans later revealed that the cancer had spread to a part of the brain, but this metastatic lesion regressed with whole-brain radiation therapy. Still, in May 2025, the man developed nausea, vomiting, and difficulty swallowing, and additional testing suggested further metastasis in the brain. A second course of IVIG provided only limited benefit.
ICIs were not reintroduced, and beginning in June 2025, the man started treatment with lurbinectedin (sold as Zepzelca), a chemotherapy approved for metastatic or extensive-stage SCLC. He developed blood-related abnormalities and inflammatory reactions, but these complications were successfully managed with supportive care, allowing treatment to continue, the team noted.
Over the following months, there was a reduction in blood abnormalities, markers of inflammation, and tumor burden, with significant clinical improvement, per the report. By the time the man was discharged in September 2025, his clinical condition was stable, and his physical function and quality of life had improved substantially from admission, the team noted.
[This case demonstrates] that individualized … therapy can effectively balance tumor control and neuromuscular recovery in complex clinical settings.
“The distinctive feature of this case is that LEMS partially improved after initial antitumor therapy but continued to relapse after discharge; however, following lurbinectedin treatment, the lung cancer did not recur, suggesting that lurbinectedin demonstrated good tumor control in this case of small-cell lung cancer complicated by LEMS,” the researchers wrote.
According to the team, this case “[demonstrates] that individualized sequential therapy can effectively balance tumor control and neuromuscular recovery in complex clinical settings.”
It also highlights that “during immunotherapy, monitoring for neurological complications and early recognition and management are of critical importance,” the team concluded.
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