GFAP and nervous system disorder: YKL‐40 is highly expressed in reactive astrocytes in brain tissue from patients with Creutzfeldt‐Jakob disease and Alzheimer's disease28, 29 and the CSF levels of YKL‐40 have been found to be elevated in several neurologic diseases with a neuroinflammatory component.28, 30, 31 The moderately elevated levels of GFAP and YKL‐40 observed in cancer survivors in the present study could potentially reflect both long‐term reactive gliosis and ongoing low‐grade neuroinflammation.