Abstract
Positron emission tomography (PET) is a highly advanced form of scintigraphy, invented for observation of regional tissue activity : glucose and oxygen consumptions, regional blood flow, neurotransmitter-receptor interactions in any part of human body. PET is currently in use not only for cancer diagnosis but also for evaluation of brain activity. Surely this functional imaging is also applicable to brain activity of cancer patients with depression. In this paper, basic concepts and techniques of PET neuroimaging in cancer patients will be overviewed, putting emphasis on its possible impacts to the field of psycho-oncology. In our study, 80 Japanese cancer patients without brain metastasis were studied with PET and ^<18>F-fluorodeoxyglucose (FDG). Regional cerebral metabolism was examined by applying statistical parametric mapping (SPM) software on their brain image extracted from their whole-body images. The brain image data of cancer patients without experience of chemotherapy were selected (19 patients) and were compared to the benign patients group. The results showed that cancer patients demonstrated decreased regional brain activity in the cingulate gyrus, prefrontal cortex, orbitofrontal cortex and so on. This finding was grossly reproduced in German cancer patients later, where 20 patients without brain metastasis were scanned by FDG-PET. Self-rating depression scales (SDS) were assigned to 16 of these patients just after the PET scanning. Cancer patients were sub-grouped by SDS scores. Comparisons were conducted between the normal and cancer patients with and without depression. The results showed that several regions were hypometabolic such as the bilateral basolateral frontal cortices, anterior and posterior cingulate gyri and right insular cortex as well as the bilateral basal ganglia, prefrontal cortices, premotor cortices and frontal eye fields. Parietal cortices also showed decreased metabolism. These regions were in accordance with our previously-reported studies on depression. These findings of hypometabolism were more intense in cancer patients with depression than those without. These results suggest that cancer patients without brain metastasis manifest abnormality in the regional cerebral metabolism and that the abnormalities in the regional metabolism may be related with their degrees of emotional disturbances. PET brain mapping of cancer patients might supply a new objective biological marker for clinical evaluation in the field of psycho-oncology.
