Dr Iams on the Importance of Anti-VGCC Antibody Testing for LEMS in SCLC

“Having a serology or a blood test that can help guide [us] to the specific diagnosis of LEMS is key, so we know that it’s not just the cancer; [patients] do have this antibody present. This opens up treatment strategies to potentially help [alleviate] the symptoms.”

Wade T. Iams, MD, assistant professor, medicine, Division of Hematology/Oncology, Vanderbilt-Ingram Cancer Center, discusses the importance of performing anti–voltage gated calcium channel (VGCC) antibody testing for a suspected diagnosis of Lambert-Eaton Myasthenic Syndrome (LEMS) for patients with small cell lung cancer (SCLC).

More than 50% of LEMS cases present as paraneoplastic LEMS, which is commonly associated with SCLC. When a patient is suspected of having LEMS, diagnoses are confirmed by serological and electrodiagnostic tests. Accordingly, one of the first diagnostic steps is ordering a paraneoplastic autoantibody panel, Iams begins. Key clinical features of this syndrome include proximal muscle weakness, autonomic dysfunction, and areflexia. The panel includes testing for the anti-VGCC antibody, which is involved in the pathophysiology of the disease. Anti-VGCC can cause a reduction in acetylcholine levels, resulting in muscle weakness. The presence of this antibody, therefore, can aid in confirming the diagnosis of LEMS, Iams says. The presence of these antibodies is particularly significant in identifying paraneoplastic LEMS, he explains. However, results from this panel can take several weeks to return, he notes.

To address this, a neurological examination is typically sought, Iams continues. Neurological evaluation will typically involve electrophysiological studies, particularly repetitive nerve stimulation (RNS). This can provide a provisional diagnosis while waiting for antibody results, he adds. These tests can identify hallmark findings of LEMS. Ultimately, early diagnosis and proper screening initiation is a priority in LEMS management, as it can improve symptom control and allow for the timely treatment initiation if a malignancy is identified. By combining serological testing with neurological evaluation, the need for diagnostic accuracy can be balanced with the urgency of initiating care, Iams concludes.