Oral 2.02: The role of postoperative radiotherapy for stage I/II/III thymic tumor—results of chart database

Background: Postoperative radiotherapy for thymic tumor is still controversial. The object of the study is to evaluate the role of postoperative radiotherapy for stage I/II/III thymic tumor.

Methods: The database of Chinese Alliance of Research for Thymomas (ChART) was retrieved for patients with stage I/II/III thymic tumor who underwent surgical therapy without neoajuvant therapy between 1994 and 2012. Univariate and multivariate survival analyses were performed. Cox proportional hazard model was used to determine the hazard ratio for death.

Results: One thousand five hundred and forty-six stage I/II/III patients were identified from ChART database. Among these patients, 649 (42.0%) underwent postoperative radiotherapy. Postoperative radiotherapy was associated with gender, histologic type [World Health Organization (WHO)], surgical extent, complete resection, Masaoka stage and adjuvant chemotherapy. The 5-year and 10-year overall survival (OS) rates and disease-free survival (DFS) rate for patients underwent surgery followed by postoperative radiotherapy were 90% and 80%, 81% and 63%, comparing with 96% and 95%, 92% and 90% for patients underwent surgery alone (P=0.001, P<0.001) respectively. The 5-year and 10-year recurrence rate for patients underwent surgery followed by postoperative radiotherapy were 18% and 35%, comparing with 7% and 8% for patients underwent surgery alone (P<0.001). In univariate analysis, age, histologic type (WHO), Masaoka stage, completeness of resection, and postoperative radiotherapy were associated with OS. Multivariable analysis showed that histologic type (WHO) (P=0.001), Masaoka stage (P=0.029) and completeness of resection (P=0.003) were independently prognostic factors of OS. In univariate analysis, myasthenia gravis, age, gender, histologic type (WHO), Masaoka stage, postoperative radiotherapy, surgical approach, tumor size and completeness of resection were associated with DFS. Multivariable analysis showed that histologic type (WHO) (P<0.001), Masaoka stage (P=0.005) and completeness of resection (P=0.006) were independently prognostic factors of DFS. Subgroup analysis showed that patients with incomplete resection underwent postoperative radiotherapy achieved better the 5-year and 10-year OS and DFS (P=0.010, 0.017, respectively). Postoperative radiotherapy did not affect the OS of patients with Masaoka stage I/II/III who underwent complete resection (P=0.067, 0.615 and 0.192, respectively).

Conclusions: The current retrospective study indicated that postoperative radiotherapy after incomplete resection could improve OS and DFS for patients with stage I/II/III thymic tumor.

Keywords: Thymic tumor; postoperative radiotherapy; survival