Significance of the Involved Organ as a Prognostic Factor in Stage III Thymomas ; a Proposal for a Novel Subclassification of Stage III Disease

Objective : The purpose of this study is to clarify the significance of the particular involved organ as a prognostic factor in stage III thymomas. Methods : The prognoses of 85 patients with stage III thymoma who underwent a complete or subtotal resection were reviewed retrospectively. Stage III disease was further categorized into 3 groups as follows ; IIIA : 15 patients with involvement of neither lung nor great vessel, IIIB : 41 patients with involvement of the lung, but not the great vessels, and IIIC : 29 patients with involvement of the great vessels irrespective of involvement of other organs. Survival was evaluated as actuarial freedom from tumor death. Results : Complete resection was performed in all patients in group IIIA, in 40 patients (98%) in group IIIB, and in 20 patients (69%) in group IIIC. The 10-year survival rate in group IIIA was 100% and there was no tumor death during the longest follw-up period of 19 years. The 20-year survival rate was 69% in group IIIB, and 33% in group IIIC. The tumor recurrence rates after complete resection were 7%, 20%, and 40% in groups IIIA, IIIB, and IIIC, respectively. The relapsed in the distant organs were frequently found in the group IIIC. Conclusion : Subclassification of stage III disease according to the involved organs was a good predictor of survival and tumor recurrence. A further improvement in the adjuvant therapy for thymomas with involvement of the great vessels seems imminent.