Long-term outcomes and patterns of failure in patients with thymic malignancies treated with surgery and radiation therapy.

Abstract

The role of peri-operative radiation therapy in thymic epithelial tumors remains controversial, and randomized data are lacking. The authors evaluated recurrence patterns, pathologic predictors of recurrence, and long-term survival among patients who underwent surgery and received peri-operative radiation at a high-volume tertiary center. The authors conducted a retrospective cohort study of patients who had thymic malignancies treated surgically between 2004 and 2021. Clinical, pathologic, and treatment data were collected. Outcomes were assessed using Kaplan-Meier and Cox regression methods, and propensity score overlap weighting was applied to adjust for baseline differences between the radiation and no-radiation groups. In total, 360 patients were included, of whom 175 (48.6%) received peri-operative radiation. Among irradiated patients, 62 (35.4%) developed recurrence, most commonly in the pleura (76%); in-field recurrences were rare (5%). Tumor invasiveness was the strongest predictor of recurrence, particularly vascular invasion (odds ratio, 6.0; 95% confidence interval, 2.3-15.7). Histologic subtype was not associated with recurrence. Survival did not differ between groups on unadjusted comparison (hazard ratio, 1.02; 95% confidence interval, 0.63-1.67; p = .93). After overlap weighting, radiation was associated with overall survival (hazard ratio, 0.49; 95% CI, 0.26-0.90; p = .02). In patients with surgically treated thymic malignancies, tumor invasiveness, especially vascular invasion, was the strongest predictor of recurrence and should guide risk stratification. Failure was predominantly pleural, with rare in-field recurrence, indicating good local control but a need for better strategies against pleural relapse. Survival benefit from peri-operative radiation remains uncertain and should be tested prospectively.