Radiation Therapy Does Not Improve the Prognosis of Patients with Stage II Thymoma, Supporting Previous Evidence Suggesting That the Presence of Transcapsular Invasion Is Not a Significant Prognostic Feature
AM Marchevsky, RS Parakh, B Hakimian. Cedars- Sinai Medical Center, Los Angeles, CA
Background: Recent metaanalysis of best available evidence showed that patients with stages I and II thymoma do not have significantly different prognosis. This suggested that detection of transcapsular invasion during the pathologic evaluation of these lesions does not provide significant prognostic information, a conclusion that was tentative because only some patients with stage II disease had been treated with radiation therapy and the possibility of treatment bias could not be excluded.
Design: A systematic review of the English literature from 1962-present was performed to identify best evidence regarding the prognostic value of radiation therapy in patients with stage II thymomas. Only studies that evaluated more than 10 patients treated with radical thymectomy, post-operative radiation therapy and provided a minimum of 5-year follow-up information were included. The level of evidence of each study was assessed using the criteria published by the Cochrane collaboration. Patients were divided into 2 groups, those that were treated with post-operative radiation therapy and those that received only thymectomy. The data was analyzed with Comprehensive Metaanalysis software (Biostat Inc Englewood, N.J.).
Results: Twenty-five level III and IV studies evaluating 1183 number of patients with stage II thymoma reported the use of post-operative radiation therapy but only 9 of these studies provided information consistent with our inclusion criteria. They reported 197 number of patients (median=24 and range 1-41) treated with radiation therapy with doses ranging from 25-72 Gy and 193 patients (median=18 and range 1-73) that were treated only with radical thymectomy. Survival proportions for patients in these two groups were 84% and 68%, respectively. Metaanalysis showed odds ratios >0.05 for the comparison of survival proportions of these two groups of patients and demonstrated the presence of significant data heterogeneity as shown by funnel plot and Egger's regression test p>0.05.
Conclusions: There is a lack of randomized clinical trials evaluating the prognosis of patients with stage II thymoma undergoing radiation therapy after complete resection.Thetreatment protocol for thymomas needs revision.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 263, Tuesday Afternoon