Objective:To analyze the invasion characteristics and prognostic factors of patients with Masaoka-Koga stage Ⅲ thymoma.Methods:The tumor invasion characteristics of 179 patients who were diagnosed with Masaoka-Koga stage Ⅲ thymoma and treated in Affiliated Cancer Hospital of Zhengzhou University from January 2000 to June 2018 were analyzed retrospectively. According to the treatment methods, all patients were divided into the radical operation group ( n=94), palliative operation group ( n=39) and simple biopsy group ( n=46). The χ2 test was used to compare the classified variables, Kaplan- Meier method was utilized to calculate the cumulative survival rate, log-rank method was used for group comparison and univariate analysis, and Cox’s regression model was used for multivariate analysis. Results:Mediastinal pleural invasion (86.0%) was the most common site, followed by pericardium (50.8%), great vessel (40.8%) and lung (36.3%). The proportion of macrovascular invasion in the radical operation group was 14.9%, significantly lower than 79.5% and 60.9% in the palliative surgery group and biopsy group (both P<0.001). Multivariate analysis showed that the nature of operation ( P<0.001), age ( P=0.011), radiotherapy ( P=0.020) were the independent factors affecting overall survival (OS), while nature of operation ( P<0.001), age ( P=0.004), radiotherapy ( P=0.020), number of invasive organs ( P=0.023) and pathological type ( P=0.016) were the independent factors affecting progress-free survival (PFS). Conclusions:For patients with Masaoka-Koga stage Ⅲ thymoma, mediastinal pleura is the most common site of invasion, pericardium, lung and great vessels are also commonly invaded. The invasion of mediastinal pleura, pericardium and lung exerts slight effect on surgical resectability, whereas great vessel involvement can significantly affect surgical resectability. OS and PFS in patients undergoing radical resection are significantly better than those in patients treated with palliative resection and biopsy. Radical resection is the most important factor affecting prognosis.

The role of definitive radiotherapy (dRT) and debulking surgery (DS) for patients with locally advanced, unresectable, Masaoka-Koga stage III thymomas was not well studied. Unresectable tumor refers to tumor that could not be completely resected because of invasion of surrounding organs. Consecutive patients with unresectable stage III thymomas between 2000 and 2017 were reviewed. According to the treatment intent and radiation dose, patients were categorized into a dRT group and a non-dRT group. The former group included patients who received radiotherapy at doses ≥ 54 Gy after DS or biopsy. The latter group included patients who did not receive radiotherapy and those who received a radiation dose < 54 Gy. A total of 82 patients were included. Compared with non-dRT, dRT significantly improved 5-year overall survival (OS, P = 0.003), progression-free survival (PFS, P = 0.008), and freedom from locoregional failure (FFLF, P < 0.001). Compared with biopsy alone, DS did not improve OS, PFS, FFLF. On multivariate analysis, dRT was an independent prognostic factor for OS (hazard ratio [HR]: 2.37, P = 0.024), PFS (HR: 2.40, P = 0.004), and FFLF (HR: 3.83, P = 0.001). In conclusion, dRT was an effective and beneficial treatment for patients with unresectable Masaoka-Koga stage III thymoma.