Associations between patient-reported outcomes and radiation dose in patients treated with radiation therapy for primary brain tumours

Aim: This study aimed to explore associations between radiation dose and patient-reported outcomes in patients with a primary non-glioblastoma brain tumour treated with radiation therapy (RT), with a focus on health-related quality-of-life (HRQoL) and self-reported cognitive function. Methods: In this cross-sectional study, 78 patients who had received RT for a non-glioblastoma primary brain tumour, underwent neumpsychological testing and completed questionnaires on HRQoL, cognitive function, fatigue, depression, anxiety and perceived stress. The study explores the association between HRQoL scores, self-reported cognitive function and radiation doses to total brain, brainstem, hippocampus, thalamus, temporal lobes and frontal lobes. In addition, we examined correlations between neuropsychological test scores and self-reported cognitive function. Results: The median time between RT and testing was 4.6 years (range 1-9 years). Patients who had received high mean radiation doses to the total brain had low HRQoL scores (Cohen's d = 0.50, p = 0.04), brainstem d = 0.65, p = 0.01) and hippocampus d = 0.66, p = 0.01). High mean doses to the total brain were also associated with low scores on self-reported cognitive functioning (Cohen's d = 0.64, p = 0.02), brainstem d = 0.55, p = 0.03), hippocampus d = 0.76, p < 0.01), temporal lobes (d = 0.70, p < 0.01) and thalamus (d = 0.64, p = 0.01). Self-reported cognitive function correlated well with neuropsychological test scores (correlation range 0.27-0.54.) Conclusions: High radiation doses to specific brain structures may be associated with impaired HRQoL and self-reported cognitive function with potentially negative implications to patients' daily lives. Patient-reported outcomes of treatment-related side-effects and their associations with radiation doses to the brain and its sub-structures may provide important information on radiation tolerance to the brain and sub-structures.