Results of radiotherapy for thymoma: retrospective cohort and propensity score matching analysis.

Objective: Thymic tumors are a rare group of anterior mediastinal tumors. Surgery is the primary treatment. Adjuvant treatment is used in select cases. The purpose of this study was to evaluate the outcomes of patients with thymic tumors, submitted or not to radiotherapy, and identify risk factors that could impact the outcomes to better support patient selection for RT.

Methods: This is a single institution retrospective cohort study. Patients with histologically proven thymoma or thymic carcinoma treated from July of 2009 to November of 2020 were included. Analysis was based on the use of radiation therapy (RT). Overall survival and disease-free survival were assessed from the date of diagnosis. To minimize selection bias, propensity score matching (PSM) regression using Kernel matching was used, estimated on the population for average treatment effect.

Results: Overall, 101 patients were analyzed, with mean age at diagnosis of 54.6 years (range 25-84 years). Unfavorable histology and more advanced stages predominated in the cohort. Nevertheless, most (69.3%) were treated with radical intent. RT was delivered in 52.9% of these patients. Five-year OS, local progression and distant progression free survivals were 81.0%, 95.0% and 88.1%, respectively for the radical intent cohort. PSM showed that RT reduced the chances of death by 6.3% (matched sample size was 60, p = 0.02).

Conclusions: In this retrospective cohort, RT had a positive impact in OS after PSM analysis. Prospective data regarding the role of RT in this disease is needed to validate these findings.