Mortality from extrathymic malignancy after thymic tumour resections: Incidences and risk factors

OBJECTIVES: To identify risk factors associated with extrathymic malignancy-related mortality after thymic epithelial tumour resection. METHODS: The Japanese Association for Research on the Thymus database registered the records of 2835 patients collected from 32 Japanese institutions from 1991 to 2010. The cumulative incidence function of death due to extrathymic malignancies or recurrence was calculated, with other causes of death as competing risks. Relevant risk factors associated with extrathymic malignancy-related deaths in patients with thymoma were evaluated using the Fine and Gray model. RESULTS: In total, 2701 patients were eligible for the analysis (thymoma, 2374; thymic carcinoma, 273; thymic neuroendocrine tumour, 54). The median follow-up period was 4.6 years. The cumulative incidence function of death due to extrathymic malignancies at 10 years was 2.2% (3.2% due to recurrence) in patients with thymoma, 1.6% (38.6% due to recurrence) in patients with thymic carcinoma and 0% (36.6% due to recurrence) in patients with thymic neuroendocrine tumour. In the multivariable analysis, age (every 10 years) at thymectomy [hazard ratio (HR) 2.19, 95% confidence interval (CI) 1.53-3.14; P < 0.001], male gender (HR 2.62, 95% CI 1.19-5.77; P = 0.017) and previous malignancies (HR 3.09, 95% CI 1.18-8.11; P = 0.022) were significant factors for death due to extrathymic malignancies after thymectomy. CONCLUSIONS: Continued management and early detection of extrathymic malignancies may improve survival of patients with thymoma who are male, of advanced age, or have previous malignancies. Prospective studies are required to further investigate the management of extrathymic malignancies.