VEGFA and pneumonitis: The clinical RT-induced pneumonitis phase manifests 3–12 weeks after RT and comprises loss of epithelial and endothelial barrier function (alveolar collapse) on the one hand, as well as vascular endothelial growth factor (VEGF)-mediated endothelial cell proliferation and pneumocyte type II proliferation for re-epithelializing the alveolar basement membrane on the other hand [3,5].