Expression of vascular endothelial growth factor receptor in thymic epithelial tumors

Thymic epithelial tumors (TETs) are rare and the major symptoms are not obvious until the tumor progresses to a relatively large size and compresses the surrounding organs. As its growth is aggressive and it metastasizes to distant organs, it is important to find novel effective therapies. Lenvatinib, a vascular endothelial growth factor receptor (VEGFR) inhibitor, is approved as a drug therapy for thymic carcinoma (TC); however, although it is a molecular targeted therapy, there are no obvious predictors of therapeutic efficacy. The present study aimed to assess the association between clinicopathological factors and the protein expression of VEGFR, which is associated with tumor aggressiveness and the efficacy of VEGFR inhibitors. The VEGFR-2 protein expression was evaluated in 144 patients with TETs who underwent surgical resection. The present study assessed whether the expression of VEGFR-2 protein was associated with TET classification and pathological stage, progression-free survival and overall survival (OS). A total of 94 cases (65.2%) were positive for VEGFR-2 protein. The expression of VEGFR-2 was higher in the more aggressive type B3 thymoma and TC (88.5%) than in types A, AB, B1 and B2 thymoma (60.2%). The 5-year OS rate for the overall population was 53.1%. The 5-year OS rates of patients with negative VEGFR-2 staining score values (66.5%) were significantly longer than in patients with positive VEGFR-2 staining score values (42.5%; P=0.000078). Furthermore, the pathological stage was the only factor significantly associated with OS in multivariate analysis. The results of the present study suggest the possibility that the indications for VEGF inhibitor therapy could be extended to type B3 thymoma.