Improved local control of chordoma initially treated with surgery or not, thanks to adjuvant radiotherapy oriented by conventional imaging Computed Tomography /Magnetic Resonance Imaging (CT / MRI) and guided by the [18Fluor] ([18F]) Fluoroazomycin Arabinofuranoside (FAZA) Positron Emission Tomography / Computed Tomography (PET / CT) to target the radioresistant hypoxic cells.