# Marked under-diagnosis of Lambert-Eaton myasthenic syndrome in small cell lung cancer: an analysis of real-world claims data

## TL;DR

This study finds that Lambert-Eaton myasthenic syndrome is under-diagnosed in patients with small cell lung cancer, based on real-world data.

## Contribution

The study reveals a significant under-diagnosis of LEMS in SCLC patients using real-world claims data.

## Key findings

- Only 0.16% of patients in a putative SCLC cohort had LEMS claims, much lower than expected.
- LEMS cases were more often diagnosed by neurologists than oncologists.
- The discrepancy suggests a need for improved recognition and management of LEMS in SCLC patients.

## Abstract

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune neurologic condition causing progressive muscle weakness that can occur as a paraneoplastic disorder, most commonly in patients with small cell lung cancer (SCLC). In limited prospective and retrospective studies, LEMS incidence in SCLC populations ranges 3-6%. Because LEMS may present a diagnostic challenge, we determined the prevalence of LEMS in a large, real-world, U.S.-based SCLC cohort.

We conducted a retrospective analysis of administrative data from Symphony Health’s PatientSource®, which represents over 300 million U.S. patients. In the primary analysis, we identified claims for LEMS (available starting in 2014) among patients with lung cancer claims between 2017 and 2022 who received etoposide and platinum-based chemotherapy (a validated approach to SCLC case identification).

Among 867,170 patients with lung cancer claims, 46,995 (5.4%) received platinum-etoposide-based therapy (putative SCLC cohort), of whom 77 (0.16%) had LEMS claims. In a subset of 8,513 patients with ≥12 months of claims preceding and following lung cancer diagnosis, 16 (0.19%) had LEMS claims. LEMS cases were more frequently diagnosed by neurologists (30%) than by oncologists (13%).

In a large real-world cohort of patients with lung cancer, LEMS is diagnosed far less frequently than would be expected and rarely by oncologists. Because LEMS may convey substantial morbidity and specific LEMS treatments are available, further efforts to understand and address this discrepancy are warranted.