Results of surgical treatment of thymomas with special reference to the involved organs

Objective: The purpose of this study is to clarify the significance of the particular involved organ as a prognostic factor and its relation to other previously reported factors. Methods: The prognoses of 194 consecutive patients with thymoma who had undergone complete or subtotal resection were reviewed retrospectively. Survival was evaluated as actuarial freedom from tumor death. Analysis of prognostic factors was performed by the Kaplan- Meier method with the log rank test and Cox's proportional hazards model. Results: The Masaoka staging system and involvement of the great vessels were the independent prognostic factors in the entire study group; age, sex, histologic subtype, completeness of resection, association of myasthenia gravis, or involvement of other organs were not factors. The 10-year and 20- year survivals were 99% and 90% in stage I, 94% and 90% in stage II, 88% and 56% in stage III, 30% and 15% in stage IVa, 0% and 0% in stage IVb, 93% and 83% in the absence of involvement of the great vessels, and 54% and 20% in the presence of it. Involvement of the great vessels was also the single independent prognostic factor in the patients with stage III disease although completeness of resection or involvement of other organs were not. The 10- year and 20-year survivals in patients with stage III disease were 97% and 75% in the absence of involvement of the great vessels, and 70% and 29% in the presence of it. Conclusion: Although the Masaoka staging system is a valuable prognostic factor, the category of stage III is heterogeneous and consists of 2 groups with distinct prognoses depending on involvement of the great vessels.