More Patients With Non-Thymomatous MG are Undergoing Thymectomy

Clinicians have performed thymectomy more often in patients with non-thymomatous myasthenia gravis (MG) since 2016, yet several disparities in thymectomy use still exist. These are the findings of a study published in Neurology: Clinical Practice.

In 2016, the phase 3 clinical trial, Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone Therapy (MGTX), found that patients with non-thymomatous MG who underwent thymectomy had lower steroid requirements, fewer received immunosuppressive treatment, they had less severe symptoms, and fewer were hospitalized than patients who did not undergo thymectomy.

Researchers from the University of Pennsylvania sourced data for this analysis from the National Inpatient Sample (NIS) which is a database of approximately 20% of discharged patients in the United States. To evaluate the uptake of thymectomy for the treatment of non-thymomatous MG, the researchers used a joinpoint regression analysis to assess trends in thymectomy between 2012 and 2019.

A total of 212,646 patients were hospitalized with non-thymomatous MG between 2012 and 2019. A total of 2% underwent thymectomy, 57% of which were trans-sternal and 43% were transcervical or video-assisted thoracic surgery (VATS) thymectomies.

The number of thymectomies increased from 45 in 2012 to 1150 in 2019, for an average annual percent change (AAPC) of 69.8%. Stratified by thymectomy type, trans-sternal thymectomies increased by 62.8% and VATS by 83.7% yearly.

In the thymectomy (age 65 and older, 21%; women, 56.9% White, 64.9%) and no thymectomy (age 65 and older, 65%; women, 51.4% White, 76.4%) cohorts, 19.3% and 52.4% had an Elixhauser Comorbidity Index (ECI) of 4 or higher, respectively.

Undergoing thymectomy was negatively related among patients aged 65 and older (adjusted odds ratio [aOR], 0.24), 55 to 64 (aOR, 0.45), or 45 to 54 (aOR, 0.59) compared with those aged 18 to 34; female gender (aOR, 0.73); Black race compared with White race (aOR, 0.62); and an ECI of 4 or more (aOR, 0.27), 3 (aOR, 0.35), or 2 (aOR, 0.61) compared with 0 or 1.

Conversely, patients with private (aOR, 2.98) or Medicaid (aOR, 1.49) insurance compared with Medicare insurance and patients treated at a large- (aOR, 2.81) or medium- (aOR, 1.82) sized hospital compared with a small hospital or at an urban teaching hospital (aOR, 6.09) compared with a rural hospital were more likely to undergo thymectomy.

This study was limited by some important clinical and demographic features that were not available in the NIS.

“[W]e found that the number of thymectomies per year increased from 2012 to 2019. This increase was especially pronounced during the final 3 years of the study period, which coincides with the publication of the MGTX trial and suggests that this event may have influenced clinical practice. […] We also found significant racial and gender disparities in thymectomy utilization for MG.”