MTOR and chordoma: Chordoma clinical trials have mainly targeted molecular pathways, such as the platelet-derived growth factor receptor (PDGFR), mammalian target of rapamycin (mTOR), BCR-ABL, KIT, vascular endothelial growth factor receptor (VEGFR), T-box transcription factor T (brachyury protein), epidermal growth factor receptor (EGFR), HER2/NEU, and topoisomerase I [39].