Zhitao Gu1, Yucheng Wei2, Jianhua Fu3, Lijie Tan4, Peng Zhang5, Yongtao Han6, Chun Chen7, Renquan Zhang8, Yin Li9, Keneng Chen10, Hezhong Chen11, Yongyu Liu12, Youbing Cui13, Yun Wang14, Liewen Pang15, Zhentao Yu16, Xinming Zhou17, Yangchun Liu18, Yi Shen2, Wentao Fang1. 1. Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China. 2. Department of Thoracic Surgery, Affiliated Hospital of Qingdao University, Qingdao, China. 3. Department of Thoracic Surgery, Guangdong Esophageal Cancer Institute, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center of Cancer Medicine, Guangzhou, China. 4. Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, China. 5. Department of Endocrinology, Tianjin Medical University General Hospital, Tianjin, China. 6. Department of Thoracic Surgery, Sichuan Cancer Hospital, Chengdu, China. 7. Department of Thoracic Surgery, Fujian Medical University Union Hospital, Fuzhou, China. 8. Department of Thoracic Surgery, First Affiliated Hospital of Anhui Medical University, Hefei, China. 9. Department of Thoracic Surgery, Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou, China. 10. Department of Thoracic Surgery, Beijing Cancer Hospital, Beijing, China. 11. Department of Cardiothoracic Surgery, Changhai Hospital, Shanghai, China. 12. Department of Thoracic Surgery, Liaoning Cancer Hospital, Shenyang, China. 13. Department of Thoracic Surgery, First Affiliated Hospital of Jilin University, Changchun, China. 14. Department of Thoracic Surgery, West China Hospital, Sichuan University, Chengdu, China. 15. Department of Thoracic Surgery, Huashan Hospital, Fudan University, Shanghai, China. 16. Department of Esophageal Cancer, Tianjin Cancer Hospital, Tianjin, China. 17. Department of Thoracic Surgery, Zhejiang Cancer Hospital, Hangzhou, China. 18. Department of Thoracic Surgery, Jiangxi People's Hospital, Nanchang, China.
Abstract
OBJECTIVES: Lymphatic involvement is believed to be relatively rare in thymic epithelial tumours. The incidence and prognostic significance of nodal metastases are still unclear. The goal of this study was to define the incidence and prognostic relevance of nodal metastasis in patients with thymic epithelial tumours, using a nationwide retrospective database of the Chinese Alliance for Research in Thymomas. METHODS: Patients who underwent upfront surgical resection without preoperative therapy were enrolled for the study. The International Thymic Malignancies Interest Group proposal of a new staging system for thymic epithelial tumours was used to redefine the pathological stage. The incidence of nodal metastasis and its relationship with clinicopathological characteristics and its impact on survival were examined accordingly. RESULTS: A total of 1617 patients were enrolled in this study. Lymph node metastasis was identified in 35 patients (2.2%). No nodal involvement was found in type A, AB or B1 thymomas. The incidence of nodal metastasis in thymoma (B2/B3) and thymic carcinoma was 1.3% and 7.9%, respectively, and it was most commonly seen in patients with neuroendocrine thymic tumours (16.7%, P < 0.001). According to the primary tumour invasion stage, incidences of nodal metastasis were 0.2% in T1, 6.9% in T2, 8.5% in T3 and 7.4% in T4 tumours (P < 0.001). Gender, pleural or distant metastasis and resection status were also correlated with nodal metastasis (P < 0.05) in univariable analysis. Multivariable analysis revealed that patients with non-thymoma histological characteristics (P < 0.001) and tumours in non-T1 stage (P < 0.001) had significantly greater risk of developing nodal metastasis. The overall survival of patients without nodal metastasis was significantly higher than that of patients with nodal involvement (P < 0.001). Disease-free survival of patients after R0 resection without nodal metastasis was also significantly higher than those with nodal metastasis (P < 0.001). On multivariable analysis, overall survival was significantly associated with histology of the tumour (P = 0.019) and complete resection (P = 0.047), and there was a trend towards significance (P = 0.052) in the association between overall survival and nodal involvement. CONCLUSIONS: Lymph node metastasis in low-grade, early stage thymic tumours is a rare phenomenon. However, it is not uncommon in tumours with a higher stage or a higher histological grade, especially in neuroendocrine thymic tumours. Nodal involvement as well as tumour invasion and histological grade may denote worse prognosis. Lymph node dissection may be warranted in selected high-risk patients.
OBJECTIVES: Lymphatic involvement is believed to be relatively rare in thymic epithelial tumours. The incidence and prognostic significance of nodal metastases are still unclear. The goal of this study was to define the incidence and prognostic relevance of nodal metastasis in patients with thymic epithelial tumours, using a nationwide retrospective database of the Chinese Alliance for Research in Thymomas. METHODS:Patients who underwent upfront surgical resection without preoperative therapy were enrolled for the study. The International Thymic Malignancies Interest Group proposal of a new staging system for thymic epithelial tumours was used to redefine the pathological stage. The incidence of nodal metastasis and its relationship with clinicopathological characteristics and its impact on survival were examined accordingly. RESULTS: A total of 1617 patients were enrolled in this study. Lymph node metastasis was identified in 35 patients (2.2%). No nodal involvement was found in type A, AB or B1 thymomas. The incidence of nodal metastasis in thymoma (B2/B3) and thymic carcinoma was 1.3% and 7.9%, respectively, and it was most commonly seen in patients with neuroendocrine thymic tumours (16.7%, P < 0.001). According to the primary tumour invasion stage, incidences of nodal metastasis were 0.2% in T1, 6.9% in T2, 8.5% in T3 and 7.4% in T4 tumours (P < 0.001). Gender, pleural or distant metastasis and resection status were also correlated with nodal metastasis (P < 0.05) in univariable analysis. Multivariable analysis revealed that patients with non-thymoma histological characteristics (P < 0.001) and tumours in non-T1 stage (P < 0.001) had significantly greater risk of developing nodal metastasis. The overall survival of patients without nodal metastasis was significantly higher than that of patients with nodal involvement (P < 0.001). Disease-free survival of patients after R0 resection without nodal metastasis was also significantly higher than those with nodal metastasis (P < 0.001). On multivariable analysis, overall survival was significantly associated with histology of the tumour (P = 0.019) and complete resection (P = 0.047), and there was a trend towards significance (P = 0.052) in the association between overall survival and nodal involvement. CONCLUSIONS: Lymph node metastasis in low-grade, early stage thymic tumours is a rare phenomenon. However, it is not uncommon in tumours with a higher stage or a higher histological grade, especially in neuroendocrine thymic tumours. Nodal involvement as well as tumour invasion and histological grade may denote worse prognosis. Lymph node dissection may be warranted in selected high-risk patients.