8572 Background: Due to lack of randomized trials, the role of postoperative radiation therapy (PORT) in thymic epithelial tumors (TET) remains controversial. This study aimed to evaluate whether PORT improves tumor control and overall survival (OS) in patients with resected TET in a large single institution database. Methods: This is a retrospective study of all TETs seen at Indiana University between 1975 and 2016. Patients with resected thymoma (T) or thymic carcinoma (TC) were eligible disregarding their margin status or stage. Study endpoints were progression free survival (PFS) and OS. Age, gender, race, tumor size, stage, pathology, grade, completeness of resection and adjuvant treatment modality were analyzed for significance on PFS and OS. Multivariate Cox model was used to identify significant factors for propensity score matching. Differences between the PORT and surgery alone group were estimated using stratified log-rank test. Results: A total of 478 patients with previous surgical resection were eligible. Masaoka Stage was: I-86 (22%); II-87 (23%); III-107 (28%); and IV-106 (27%), respectively. Multivariate analysis demonstrated that gender (HR = 1.4, p = 0.03), stage (HR = 1.3, p = 3×10-3), TC (HR = 1.6, p = 0.03) and PORT (HR = 1.6, p = 0.002) were significantly associated with PFS. Age (HR = 1.1, p = 4×10-7), TC (HR = 3.2, p = 3×10-5), stage (HR = 1.4, p = 0.003) were associated with OS. PORT was given to 126 (26%) patients. Propensity score matching based on independent prognostic factors identified 99 patients for PORT, matched to 285 patients without. The 5-/10-year intra-thoracic progression free rates were 77%/69% and 85%/68%, for patients with and without PORT (p = 0.009), respectively. The 5-/10-year PFS rates were 39%/18% and 61%/32%, for patients with and without PORT (p = 0.002), respectively. The median survival, 5-/10-year OS rates for patients treated with PORT were 150 (95%CI 111~277) months, 87%/57% and respectively, compared to 192 months (95%CI 167~279), 88%/69% for patients receiving surgery alone ( p = 0.13). Conclusions: This matched-paired analysis from a single institution suggests that PORT does not impact the PFS or OS in a selected population of resected TET.
Epidemiology of thymic epithelial tumors: 22‐years experience from a single‐institution
