Evaluation of the effects of chronic stress on brain metabolism and volume in oncology patients using 18FDG-PET/MR

Objective: The presence of cancer itself is a significant source of stress. Additionally, concerns about treatment outcomes, fear of the future, and uncertainty in cancer patients can result in stress and anxiety. In our study, we aimed to evaluate the effects of chronic stress on cognitive and behavioral functions of the brain at a molecular-anatomical level in an oncology patient group. Materials and Methods: 64 patients with a cancer diagnosis and additional 11 control subjects with no malignant disease who were referred to the Department of Nuclear Medicine, Cerrahpaşa Faculty of Medicine for performing whole-body fluorine-18-labeled fluorodeoxyglucose (FDG)-Positron Emission Tomography (PET) imaging were included in the study. The Perceived Stress Scale (PSS) survey was obtained from the patients with cancer diagnosis before imaging. Following routine whole-body FDG-PET scans, all participants also underwent brain dedicated FDG-PET imaging on the Magnetic Resonance (MR) integrated PET scanner (PET/MR). The obtained PET and MR data-sets were analysed with Statistical Parametric Mapping (SPM) software to investigate regional brain metabolism and morphological changes on the basis of voxel clusters. Statistical differences were assessed between the patients and control group data, as well as between subgroup of the patients including PSS scoring equal to or above 28 and below 28, metastatic and non-metastatic groups, and the diagnosis time less than 5 years and more than 5 years in the patients subgroup with high PSS scoring. Results: In the patient group, there were significantly hypometabolic voxel clusters in the right superior parietal lobule, right inferior occipital gyrus, and left fusiform gyrus compared to the control group. The comparison between the PSS score 28 and above versus below 28 groups revealed significant hypometabolic regions in the left posterior cingulate and right parahippocampal gyrus in the high PSS score group. Metastatic patients showed significant hypometabolism in the right angular gyrus, right precuneus, and right posterior cingulate gyrus comparing to non-metastatic group. Duration-related analysis conducted in high PSS score group demonstrated no hypometabolic area in the patients who diagnosed older more than 5 years, whereas there were hypometabolism in the right inferior occipital gyrus, right superior parietal lobule, and right fusiform gyrus in the group with the disease diagnosis less than 5 years. No hypermetabolic area was found in none of the patients subgroups. VBM analysis on MR data revealed a volume decrease in the left orbitofrontal gyrus, right hippocampus, right parasagittal gyrus, and both thalami in the patient group compared to the controls. No significant volume changing was found in the comparisons of patients subgroups. Also there was no area with volume increase in any subgroup. Conclusion: We were to able to demonstrate some metabolic and morphological changes on the human brain by using a brain dedicated FDG-PET/MR imaging, most probably induced by cancer diagnosis itself in the oncological patients. We thought that these changes would play an active role in the sight of pathophysiology of the disease and even may have a prognostic effect. In this context, we think that brain dedicated FDG-PET/MR study in addition to routine whole-body PET imaging in oncological patients in the centers where PET/MR facility is available would be beneficial for the clinicians in the effective patient management.