Postoperative Radiotherapy for Completely Resected Masaoka/Masaoka-Koga Stage II/III Thymoma Improves Overall Survival: An Updated Meta-Analysis of 4746 Patients

Our systematic review and meta-analysis aimed to evaluate the effect of postoperative radiotherapy (PORT) on completely resected Masaoka/Masaoka-Koga (M/MK) stage II/III thymomas. We systematically searched four online databases and included studies that compared surgery alone versus surgery plus a PORT for completely resected M/MK stage II/III thymoma. The multivariate-adjusted hazard ratios (HRs) of overall survival (OS) and disease-free survival were evaluated as the primary and secondary end points, respectively. We performed a subgroup analysis for OS with respect to M/MK stage II, III, and inseparable II/III cases. A generic inverse variance meta-analysis using a random model was conducted. Five studies including 4746 patients (among them, 2408 patients received PORT) met our selection criteria. A meta-analysis of these five studies revealed that PORT was associated with a significantly better OS (HR = 0.68, 95% confidence interval [CI]: 0.57–0.83, p < 0.001, I2 = 0%, p for heterogeneity = 0.97). Subgroup analyses for M/MK stage II disease (HR = 0.63, 95% CI: 0.44–0.91, p = 0.01, I2 = 0%, p for heterogeneity = 0.80) and M/MK stage III disease (HR = 0.72, 95% CI: 0.55–0.95, p = 0.02, I2 = 0%, p for heterogeneity = 0.84) revealed similar results. PORT was not associated with an improved disease-free survival (HR = 0.96, 95% CI: 0.70–1.33, p = 0.83, I2 = 0%, p for heterogeneity = 0.72). Currently available evidence from observational studies suggests PORT for patients with completely resected M/MK stage II/III thymoma. A randomized trial is warranted.