Cognitive Decline following Radiotherapy of Head and Neck Cancer: Systematic Review and Meta-Analysis of MRI Correlates

SIMPLE SUMMARY: Patients with nasopharyngeal carcinoma (NPC) following radiotherapy may show decline in their cognitive abilities. Early detection is essential for accurate treatment and prevention of cognitive decline. Our review is the first meta-analysis on the correlates between cognitive impairment and brain structural and functional changes. The review also showed that neuropsychological tests together with magnetic resonance imaging biomarkers have the potential to predict and monitor cognitive decline. In addition, cognitive decline following radiotherapy of head and neck cancer is dose-dependent with changes in brain imaging. ABSTRACT: Radiotherapy for head and neck cancers exposes small parts of the brain to radiation, resulting in radiation-induced changes in cerebral tissue. In this review, we determine the correlation between cognitive deterioration in patients with head and neck cancer after radiotherapy and magnetic resonance imaging (MRI) changes. Systematic searches were performed in PubMed, Scopus, and Cochrane databases in February 2021. Studies of head and neck cancer patients treated with radiotherapy and periodical cognitive and MRI assessments were included. Meta-analysis was performed to analyse the correlation of Montreal Cognitive Assessment (MoCA) scores to MRI structural and functional changes. Seven studies with a total of 404 subjects (irradiated head and neck patients, n = 344; healthy control, n = 60) were included. Most studies showed the significance of MRI in detecting microstructural and functional changes in association with neurocognitive function. The changes were seen in various brain areas, predominantly the temporal region, which also shows dose dependency (6/7 studies). An effect size (r = 0.43, p < 0.001) was reported on the correlation of MoCA scores to MRI structural and functional changes with significant correlations shown among patients treated with head and neck radiotherapy. However, the effect size appears modest.