The Impact of Postoperative Radiation Therapy (PORT) on the Overall Survival (OS) of Completely Resected Masaoka/Masaoka-Koga Stage II Thymoma: An Updated Meta-Analysis

Abstract

The benefit of PORT in patients with completely resected stage II Thymoma has been controversial. Two separate meta-analyses were conducted in 2015 and 2016 to address this uncertainty. The former revealed no survival benefit to PORT in stage II. However, the latter, which was methodologically flawed, revealed an increased survival in a combined cohort of stage II & III. The purpose of this meta-analysis is to evaluate the impact of PORT on OS in patients with completely resected Masaoka or Masaoka-Koga strictly stage II Thymoma incorporating more recent studies. A review of the medical literature was conducted using online databases. Inclusion criteria consisted of (i) resected Masaoka stage II Thymoma (ii) English language (iii) studies reporting OS with hazard ratios (HR) or Kaplan-Meier curves, and (iv) OS data on patients that underwent PORT versus those that did not. Studies that combined stage II with other stages and those that combined Thymoma with Thymic carcinoma were excluded. A meta-analysis was conducted using an inverse variance method with random-effects model. Seven retrospective series with a total of 2828 patients were included and analyzed. Three of these studies analyzed their data using stage IIB as a separate category while the remaining 4 analyzed stage II as whole. PORT was found to be significantly associated with OS benefit in patients with completely resected stage II Thymoma (HR 0.77, 95%CI 0.71-0.84; I2 = 0%). This is the first meta-analysis to show that PORT is associated with survival benefit in patients with completely resected Masaoka/Masaoka-Koga stage II/IIB Thymoma using studies that reported OS data distinctly for stage II. In the absence of randomized clinical trials, it represents the most compelling data supporting the use of PORT in this patient population.