Postoperative Radiation Therapy for Thymic Carcinoma: An Analysis of the International Thymic Malignancy Interest Group/European Society of Thoracic Surgeons Database

Introduction: R0 resection and radiation therapy have been associated with improved overall survival (OS) in patients with thymic carcinoma (TC). Here, we analyzed which subgroups of patients derive the greatest benefit from postoperative radiation therapy (PORT). Methods: Clinical, pathologic, treatment, and survival information of 462 patients with TC from the International Thymic Malignancy Interest Group/European Society of Thoracic Surgeons database were analyzed. Variables included age, sex, continent of treatment, paraneoplastic syndrome, carcinoma subtype, tumor size, pathologic Masaoka stage, resection status, and use of chemotherapy. OS was the primary end point using the Kaplan-Meier method. Time to recurrence (TTR) was the secondary end point using a competing risk analysis. A 3-month landmark analysis was performed. Results: PORT was associated with a significant OS benefit (5-y OS 68% versus 53%, p = 0.002). In patients with R0 resection, PORT was associated with increased OS for advanced (stages III–IV, p = 0.04), but not early (stages I–II, p = 0.14) stage TC. In patients with an R1/2 resection of advanced-stage TC, PORT was associated with significantly longer OS (5-y OS 53% versus 38%; p < 0.001). Subset analyses did not reveal clear associations of PORT with TTR. On multivariable analysis, lower pathologic stage, PORT, and R0 resection status were associated with an OS benefit, whereas only higher age and lower pathologic stage had an association with longer TTR. Conclusions: In the largest individual patient data set on patients with TC reported to date, PORT was associated with a meaningful OS benefit in patients with advanced-stage TC after an R0 or R1/2 resection.