Long-term outcome and prognostic factors of surgically treated thymic carcinoma: Results of 306 cases from a Japanese nationwide database study

OBJECTIVES: Thymic carcinoma is a rare thymic malignancy. The purpose of this study was to evaluate the prognostic impact of clinicopathological variables and perioperative therapy for surgically treated thymic carcinoma using a nationwide database. METHODS: Of 2835 patients with surgically treated thymic epithelial tumours collected from 32 Japanese institutions, a total of 306 patients with thymic carcinomas, excluding neuroendocrine tumours, were enrolled in this retrospective study. Multivariable Cox regression analyses were performed for overall (OS) and recurrence-free survival (RFS) after R0 resection. RESULTS: Of 306 patients, 228 (75%) patients presented with Masaoka stage III-IV. Squamous cell carcinoma was the most common histological type (n = 216, 71%). R0 resection was performed in 181 (61%) patients, R1 in 46 (16%), R2 sub-total (≥ 80% tumour resection) in 43 (14%) and R2 non-resection in 27 (9%). The 5-year OS rate was 61%. Prognostic factors for OS were Masaoka stage and resection status. R0 resection was associated with most improved OS; however, both R1 and R2 sub-total resection resulted in superior OS compared with R2 non-resection [hazard ratio (95% confidence interval) for R0, R1 and R2 sub-total, 0.27 (0.15-0.48), 0.40 (0.22-0.74) and 0.38 (0.20-0.72), respectively]. Histological type and perioperative therapy did not affect OS, whereas tumour size and postoperative radiotherapy were associated with improved RFS after R0 resection. CONCLUSIONS: R0 resection is essential for prolonged OS for surgically treated thymic carcinoma, but maximal debulking surgery might be beneficial and worth evaluating for advanced disease deemed difficult for R0 resection. The benefit of postoperative radiotherapy after R0 resection should also be evaluated prospectively.