Modified maximal thymectomy for thymic epithelial tumors: predictors of survival and neurological outcome in patients with thymomatous myasthenia gravis.

BACKGROUND: Thymic epithelial tumors are characterized by slow growth and variable malignant behavior. We present our experience on the surgical management of these tumors.
MATERIALS AND METHODS: We conducted a retrospective analysis of patients with thymomas undergoing modified maximal thymectomy over a period of 16 years. Evaluated parameters included gender, age, Masaoka stage, WHO histology, R0 resection, myasthenia gravis, and adjuvant radiotherapy. In thymoma-associated myasthenia gravis, further analysis was made according the Osserman stage, the time from myasthenia diagnosis to thymectomy, and the steroid treatment. End points were survival for the total study group and achievement of complete stable remission (CSR) in patients with myasthenia gravis.
RESULTS: The study group consisted of 15 male and 24 female patients. There was no perioperative mortality. Overall survival was 91.6% and 75.1% at 5 and 10 years. Univariate analysis identified the following predictors of survival: myasthenia (P < 0.001), Masaoka stage (P < 0.001), R0 resection (P < 0.001), and WHO histology (P = 0.007). Only the WHO histology was an independent predictor of survival in multivariate analysis (P = 0.003). Myasthenia patients had CSR prediction of 51.9% and 75.9% at 10 and 15 years. Preoperative steroid treatment (P = 0.007) and WHO histology (P = 0.021) were independent predictors of CSR on multivariate analysis.
CONCLUSIONS: Modified maximal thymectomy is safe and efficient in the treatment of thymomas. WHO histology is the prime determinant of tumor aggressiveness and patient survival. Paraneoplastic myasthenia gravis and its outcome after thymectomy is significantly correlated with the WHO classification subtypes; however, lower CSR rates are not necessarily associated with more aggressive histological subgroups.