Background:Nasopharyngeal carcinoma (NPC) is sensitive to radiotherapy (RT).However,neurocognitive complications such as memory loss and leing and attention deficits emerge in the survivors of NPC who received RT.It remains unclear how radiation affects patient brain function.This pilot study aimed at finding cerebral functional alterations in NPC patients who have received RT.Methods:From September 2014 to December 2016,42 individuals,including 22 NPC patients and 20 normal volunteer controls in National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital,Chinese Academy of Medical Sciences,and Peking Union Medical College,were recruited in this study.All patients received resting-state functional magnetic resonance imaging scans and neurocognitive tests 1 day before the initiation of RT (baseline) and 1 day after the completion of RT;the 20 normal controls were also subjected to the same scans and tests.The amplitude of the low-frequency fluctuations (ALFF) in blood oxygen level-dependent signals and functional connectivity (FC) were used to characterize cerebral functional changes.Independent t test,paired t test,and analysis of variances were used to obtain statistical significance across groups.Results:After RT,NPC patients showed significantly decreased ALFF values in the calcarine sulcus,lingual gyrus,cuneus,and superior occipital gyrus and showed significantly reduced FC mainly in the default mode network (P ＜ 0.05,corrected by AlphaSim).Relative to the controls,ALFF was decreased in the lingual gyrus,calcarine sulcus,cingulate cortex,medial prefrontal gyrus (P ＜ 0.05,corrected by AlphaSim),and FC reduction was found in multiple cerebellar-cerebral regions,including the cerebellum,parahippocampus,hippocampus,fusiform gyrus,inferior frontal gyrus,inferior occipital gyrus,precuneus,and cingulate cortex (P ＜ 0.001,corrected by AlphaSim).Conclusions:Cerebral functional alterations occur immediately after RT.This study may provide an explanation for the cognitive deficits in the morphologically normal-appearing brains of NPC patients after RT and may contribute to the understanding of the complex mechanism of RT.