| Aim: As the most common anterior mediastinal tumor with a very rare incidence,thymoma is controversial with respect to the clinical stages assignment and currentpathology classifications becaus pathologically indolent cases often show invading,recurrent or metastatic malignancies. Therefore,certain markers should be defined asa complement of clinicopathological parameters to evaluate malignancy andoutcome, especially prior to the assignment of a therapy.Epidermal growth factorreceptor (EGFR), a cellular surface membrane glycoprotein receptor, plays a keyrole in the regulation of key normal cellular processes and in the hyperproliferation,metastasis epithelium-derived,infiltration and invasion tumors as a cellular surfacemembrane glycoprotein receptor. EGFR up-regulation in thymoma has been reportedin previous studies. Accordingly,we speculated EGFR plays a key role in theprogression of this disease. In this study, the expression of EGFR in thymoma wastested using an immunohistochemical assay. Correlations between EGFR andclinicopathological characteristics were analyzed and the survival rate wasinvestigated.Methods: A total of20thymic hyperplasia and63thymoma patients were recruitedto performe immunohistochemical assays to evaluate epidermal growth factorreceptor expression. The patients were pathologically diagnosed between2002and2006in the First Affiliated Hospital of Nanjing Medical University, and the63thymoma patients were available for a5-year follow-up study.15patients were lostat follow-up and3patients succumbed to diseases of other systems,a total of45 cases were available for the5-year survival. A number of factors, includingpathological classification, clinical stage, EGFR expression, and completed resection,were considered for the multivariate analysis. The multivariate analysis, conductedwith the application of Cox regression, was used to evaluate the effect of the selectedprognostic factors on survival. Relapse-free curves were analyzed by theKaplan-Meier method and compared using the log-rank test.Results: EGFR is not correlated with age, gender or myasthenia gravis morbidity(p>0.05).The results of thymic hyperplasia and thymoma were significantly differentfrom those of EGFR（p=0.006）.EGFR was found to correlate with tumor size（p=0.021）.The positive rates in the various types of thymoma were significantlydifferent (p<0.05, r=0.412). Regarding the rank correlation between the positiverates and different clinical stages, a statistical significance was noted among therespective stages (p<0.05) with a moderate relativity (r=0.534).The Cox regressionmodel showed that only clinical stages significantly affected overall survival(p=0.02<0.05) among the potential factors. EGFR is not shown to be an independentprognostic factor of thymoma;however, a significant difference was noted in therelapse-free survival time between the EGFR-negative and EGFR-positive groups.Conclusion: The prevalence of EGFR is well-correlated with the pathological typing,clinical staging and tumor size. The present follow-up data that the completelyresected cases with EGFR expression showed a significantly higher relapse rate thanthe negative group in stage Ⅱsuggest EGFR plays a key role in progression ofthymoma.EGFR may can be used to predict prognosis of thymoma and help makeaccurate diagnosis. A number of trials on the application of EGFR-targeted agents in advanced thymoma cases showed a favorable response.If EGFR-targeted agents areconfirmed to be useful in thymoma, particularly for preoperative neo-adjuvantchemotherapy, tumor size may be reduced and complete resection or even survivalrate may increase.If we could confirm the prognostic significance of EGFRexpression in thymoma，we can design more rational surgery programs or moreprivate chemo-and radiotherapy protocols,such as thoracoscopic surgery which canreduce the loss of blood and hospitalization time. |
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