Thymoma - the usefulness of some prognostic factors for diagnosis and surgical treatment

Aims: The aim of the study was to identify prognostic factors which could help evaluate both the treatment offered to patients with thymoma and late results. Methods: Forty patients were treated for mediastinal thymoma. The patients were staged clinico-pathologically (according to Masaoka) on the basis of the retrospective analysis of their operation protocols as follows: seven (17.5%)-stage I, 19 (22.5%)-stage II, 17 (42.5%)-stage III, seven (17.5%)-stage IV. Analysis of DNA contents in cell nuclei of 23 thymomas was performed by the flow cytofluorometric method. Results: From the whole group of patients, 65% survived for 5 years, 55% survived for 10 years and 43% survived for 15 years. We noted significant differences in survival time between stage I and stage IV (P<0.0012); stage II and stage IV (P<0.0006), as well as between stage III and stage IV (P<0.005). Significantly worse prognosis was observed in the case of cortical thymomas as compared with medullary or mixed types (P<0.0001; P<0.002). Analysis of DNA content showed signficantly higher probability of survival for the patients who had DI=1.0 (diploid), as compared with DNA >1.0 (aneuploid) (P<0.006). Of the 11 patients with diploid tumours, 91% survived for 5 years, but of the 12 aneuploid, only 23% survived. Conclusion: The most important positive prognostic factors influencing survival rate in patients with thymoma are: lower stage, medullary type (according to Muller-Hermelink classification), possibility of performing complete resection, diploidal nature of the tumour. Multivariate analysis of survival revealed clinico-pathological stage (according to Masaoka) and histological type (according to Salyer) as significantly independent prognostic factors.