VEGFC and cancer: Experiments on HNSCC cell lines allowed to prove that mRNA levels of genes involved in angiogenesis, inflammation, proliferation, and anti-tumor immunity are significantly lower after PT; indeed, while both proton and photon irradiation are known to increase the vascular endothelial growth factor C (VEGF-C), a key factor linked to the metastatic dissemination of cancer cells and unfavorable prognosis, and proton exposure results in significantly reduced levels [57].