Thymomectomy versus complete thymectomy in early-stage non-myasthenic thymomas: a multicentric propensity score-matched study

Objectives: Thymomectomy is gaining consensus over complete thymectomy in early-stage thymoma without myasthenia gravis. This is due both to the difficulty of establishing prospective and randomized controlled studies and to the lack of well-defined selection criteria. This bicentric, retrospective propensity score-matched study aims at comparing oncological outcomes, measured in terms of overall survival and thymoma-related survival, in patients undergoing either thymomectomy or complete thymectomy. Methods: We retrospectively analysed medical records of patients with clinical early-stage (I and II) thymoma undergoing thymomectomy or complete thymectomy. Exclusion criteria were the presence of myasthenia gravis, clinical advanced tumours and thymic carcinoma. A propensity score-matching analysis was applied to reduce potential preoperative selection biases such as comorbidity (Charlson score), tumour maximal diameter and surgical approach (open versus minimal). All variables were dichotomized. Results: A total of 255 patients were enrolled from 2 different Hospitals, 126 underwent complete thymectomy and 129 a thymomectomy. Disease-free and thymoma-related survivals showed a 5-year rate of 87.7% and 96.0% and a 10-year rate of 82.2% and 91.9%, respectively. Propensity score-matching analysis selected a total of 176 patients equally divided between the 2 groups. No difference was found for both disease-free (P = 0.11) and thymoma-related (P = 0.37) survival in the 2 groups of resection. Multivariable Cox regression analysis showed that histology (P < 0.001), residual disease (P < 0.001) and adjuvant chemotherapy (P < 0.001) were the only predictors of shorter disease-free survival. Whereas there was no evidence to confirm that disease-free and thymoma-related survivals were influenced by resection extent. Conclusions: Thymomectomy is an adequate surgical resection for non-myasthenic thymoma, achieving disease-free and thymoma-related survivals comparable to those after complete thymectomy.