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High-dose intensity-modulated radiotherapy (IMRT) has led to excellent prognosis in patients with localized nasopharyngeal carcinoma (NPC). Given the relatively young age of onset and the close anatomic relationship between the nasopharynx and the central nervous system, post-radiation neurocognitive impairment among long-term survivors represents an under-recognized late complication. This study aims to determine the prevalence and the affected cognitive domains in post-IMRT NPC survivors. We undertook a cross-sectional study in a high-volume tertiary oncology center in Hong Kong. NPC survivors who underwent IMRT with a minimal post-radiotherapy interval of 1 year were eligible. All patients underwent an initial screening using the Montreal Cognitive Assessment-Hong Kong (MoCA-HK) test, followed by a 2-hour comprehensive battery of neurocognitive assessments covering 8 distinct domains: intellectual capacity (WAIS-IV), attention span (WAIS-IV digit span, WMS-III Visual Spatial Span), visual memory (WMS-III Visual reproduction span), verbal memory (Auditory Verbal Learning Test), processing speed (Color Trail Test), executive function (Stroop Test), motor dexterity (Grooved Pegboard Test) and language ability (Verbal Fluency Test). Mean percentiles and Z-scores of all neurocognitive assessments were compared with age- and/or education-matched population normative data using one-sample t-tests. Correlation of cognitive outcomes with clinical factors were analyzed using multivariable linear regression. A total of 182 NPC survivors were enrolled. The median post-radiotherapy interval was 6.9 years, 129 (70.9%) were long-term survivors at least 5 years beyond radiotherapy. The median age was 56 years old, 89% of the enrolled patients had stage III-IVA NPC by AJCC/UICC 8th Edition, and 87% of patients received chemotherapy. The mean MoCA score was 23.6, 25.8% of patients were considered cognitively impaired. NPC survivors demonstrated significant cognitive impairment in verbal memory (p<0.001), processing speed (p<0.001), executive function (p<0.001), motor dexterity (p<0.001) and language ability (p=0.001). Most significant impairment was observed in executive function, mean z-scores of which were -1.76 to -1.38 below normative data. Post-IMRT interval, disease stage and chemotherapy usage showed no significant association with the degree of neurocognitive impairment. Post-IMRT neurocognitive impairment was prevalent in NPC survivors. Neurocognitive function was not impaired globally but occurred predominantly in selected domains, particularly executive function. Cognitive assessment and training should be considered a part of survivorship care for NPC patients. Future research on the correlation between neurocognitive function and radiation dosimetry of various brain subsites would be informative. [ABSTRACT FROM AUTHOR]