Prognostic and Therapeutic Markers in Chordomas: A Study of 287 Tumors

Abstract

Chordomas are slow-growing malignant neoplasms. Determination of histopathologic prognostic factors using a large cohort study has been limited by their low incidence. In this retrospective study, we investigated the clinical, histopathologic, and immunohistochemical prognostic factors in 287 chordomas from 111 patients assessed by central pathologic review. Expression patterns of a variety of markers, including vascular endothelial growth factor (VEGF), mTOR pathway, c-kit, HER2, epidermal growth factor receptor (EGFR) and STAT3, and KRAS, BRAF, EGFR, and PIK3CA mutations were analyzed. On univariate analysis, the results confirm surgery as the best treatment, as judged by patient progression-free survival (PFS) and overall survival (OS). Proton therapy, the presence of a dedifferentiated component, mitotic figures, and Ki67 and p53 labeling indices correlated with PFS. Necrosis and apoptosis correlated with OS. Based on these findings, we propose a histopathologic grading system that correlates with PFS and OS. On multivariate analysis, extent of resection, tumor grade, and proton therapy were independent prognostic factors of PFS; extent of resection, tumor location, and grade were independent prognostic factors of OS. Based on the expression of EGFR, pSTAT3, VEGF, and mTOR pathway proteins, (in 85.9%, 79.1%, 85.7%, and 46% of chordomas, respectively), and 2 new mutations in the PIK3CA gene, we also provide evidence for potential therapeutic targets.