Association of Center-Level Operative Volume with Outcomes Following Thymectomy

S. Kim¹, N. Cho², J. Hadaya³, S. Sakowitz⁴, S. Mallick¹, J. Curry³, K. Ali¹, P. Benharash^5
1UCLA, Los Angeles, California ²David Geffen School of Medicine, Los Angeles, California ³David Geffen School of Medicine at UCLA, Los Angeles, California ⁴UCLA David Geffen School of Medicine, Los Angeles, California ⁵UCLA Division of Cardiac Surgery, Los Angeles, California

Purpose: Surgical resection remains the standard treatment option for patients with thymoma and select cases of myasthenia gravis.1,2 Despite its proven efficacy, the impact of hospital characteristics on clinical outcomes of this operation remains understudied. The present work evaluated the association of center-level thoracic operative caseload with outcomes of thymectomy.

Methods: All elective adult hospitalizations for major thoracic operations (esophagectomy, lobectomy, mediastinal resection, thymectomy and segmentectomy) were queried from the 2016-2020 Nationwide Readmission Database. The hospital thoracic caseload was calculated as the number of overall major thoracic operations performed each year. Similarly, thymectomy volume was determined by number of such cases performed annually at each institution. Major adverse events (MAE) were defined as a composite of in-hospital mortality and neurologic, cardiovascular, respiratory, thromboembolic, and infectious complications. A logistic regression model for MAE was developed with overall thoracic operation case volume treated as a restricted cubic spline. The overall thoracic caseload corresponding to the inflection point of the spline was used to stratify centers as high-(HVH) and low-volume hospitals (LVH). Entropy balancing was used to account for intergroup differences. A doubly-robust multivariable regression was used to examine the association of HVH status with MAE, duration of hospitalization, costs and 30-day nonelective readmissions.

Results: Of an estimated 16,778 patients, 2,176 (13.0%) underwent thymectomy at HVH. Compared with those undergoing thymectomy at LVH, patients at HVH were comparable in distribution of age (57 [44-67] vs 58years [43-67], P=0.82), sex (Female: 55.0 vs 54.3%, P=0.65), and burden of comorbidities as measured by the Elixhauser Comorbidity Index (2 [1-3] vs 2 [1-3], P=0.06). Patients at HVH were more commonly insured by private payers (56.0 vs 48.1%, P< 0.001).
Following spline analysis, we observed a nonlinear, inverse relationship between hospital thoracic operative volume and MAE, with an inflection point at 188 cases (Figure 1A). Using this threshold, risk-adjusted analysis demonstrated HVH status to be associated with reduced odds of MAE (Adjusted Odds Ratio [AOR] 0.72, 95% Confidence Interval [95% CI] 0.58-0.89, P=0.003). Both an increase in institutional thymectomy and overall thoracic operation volume were independently associated with lower odds of MAE (Figure 1B). Furthermore, HVH status was associated with reduced odds of respiratory complications (AOR 0.69, 95% CI 0.56-0.86, P=0.001). Both hospitalization costs and duration of stay were not associated with HVH status. Management at HVH was associated with reduced odds of 30-day nonelective readmission (AOR 0.70, 95% CI 0.54-0.92, P=0.01).

Conclusion: Our study highlights the synergistic association of increasing overall thoracic operative and procedure-specific volumes with a marked reduction in MAE following thymectomy. Volume standards aimed at enhancing quality of care should consider both metrics as potential avenues to improve acute outcomes in patients receiving thymectomy.

Identify the source of the funding for this research project: N/A