¹⁸F-FDG PET/CT Study On The Changes Of Brain FDG Metabolism In Patients With DLBCL After Chemotherapy

Objective The aim of the study was to retrospectively analysis the 18F-FDG PET cerebral data of patients with diffuse large B-cell lymphoma(DLBCL),and to illustrate the brain glucose metabolism changing pattern in DLBCL patients.Relationships between cerebral glucose metabolism and total lesion glycolysis(TLG),clinical staging,chemotherapy cycles and the date between PET/CT and off chemotherapy were also explored.Methods Forty-five DLBCL who underwent two 18F-FDG PET/CT examinations at baseline and after chemotherapy(9 patients after 4 chemotherapy cycles,26 patients after 6 cycles,10 patients after 8 cycles)were enrolled in this study(DLBCL group)and 29 healthy controls matched in sex and age(control group).All patients with DLBCL received standard chemotherapy with CHOP or R-CHOP regimen.The general clinical data of the patients were recorded,such as clinical stage,chemotherapy cycle,time to stop chemotherapy and so on.The American GE company Discovery VCT 64 PET/CT carries on the image acquisition.1.The voxel-to-voxel SPM8 statistical analysis was carried out between the baseline brain PET images of the DLBCL group and the control group,and the brain regions with statistical difference in glucose metabolism between DLBCL patients and normal subjects were obtained.2.SPM8 statistical analysis was used to obtain the difference of brain glucose metabolism between patients with stage I and II in DLBCL group and patients with stage III and IV.3.Based on the preprocessing of statistical parameter map and Sc An VP ALL template,the brain was divided into 120 symmetrical brain regions.The relative glucose metabolic rate of each brain region in DLBCL group before and after chemotherapy was calculated,and the semi-quantitative values of metabolic differences in different brain regions were compared.4.The TLG value was obtained by using AW4.4 workstation and PET VCAR.SPSS 17.0 software was used for statistical analysis: in the DLBCL group,the relative glucose metabolic rate of each brain region before and after chemotherapy was analyzed by paired t test,and the statistically significant brain regions were analyzed by Pearson correlation with TLG,clinical stage,chemotherapy cycle and the date between PET/CT and off chemotherapy.p < 0.05 means the difference is statistically significant.Results 1.The glucose metabolism in the right superior temporal gyrus and middle temporal gyrus(BA39)in the DLBCL group was lower than that in the control group.2.There was no significant difference in brain glucose metabolism between DLBCL stage I and II stage patients and III and IV stage patients(p < 0.05).3.After chemotherapy,the brain regions with decreased relative glucose metabolic rate included prefrontal cortex(left orbital inferior frontal gyrus,right straight gyrus),limbic system(bilateral temporal poles,right anterior cingulate and lateral cingulate gyrus,bilateral hippocampus,bilateral parahippocampal gyrus,bilateral amygdala,right thalamus),bilateral olfactory cortex,bilateral pons,cerebellum(left cerebellar peduncle,cerebellar vermis,bilateral cerebellar hemispheres)(p < 0.05).After chemotherapy,The brain regions with higher relative glucose metabolic rate included bilateral occipital lobe(bilateral superior occipital gyrus,middle and inferior occipital gyrus,bilateral cuneate gyrus),bilateral parietal gyrus(bilateral superior parietal gyrus,bilateral angular gyrus,bilateral postcentral gyrus,bilateral cuneate anterior lobe,bilateral inferior parietal angular gyrus),frontal lobe(right precentral gyrus,right deltoid frontal gyrus,right inferior frontal gyrus,right middle frontal gyrus),bilateral peritalar fissure cortex(p < 0.05).The difference of relative glucose metabolic rate after chemotherapy in 4.DLBCL group had nothing to do with TLG,clinical stage and chemotherapy cycle.The relative glucose metabolic rate of right straight gyrus and left middle occipital gyrus was negatively correlated with the date between PET/CT and off chemotherapy(p < 0.05).Conclusion The decrease of metabolism in prefrontal lobe and limbic system(including hippocampus and parahippocampal gyrus)after chemotherapy may be related to the change of cognitive function of the patients.the increased metabolism of occipital lobe and parietal lobe and the decrease of metabolism in part of temporal lobe may be related to the changes of neuropsychiatric state of patients.The changes of 18F-FDG metabolism in brain area after chemotherapy are related to the function and anatomical location of brain region.Understanding the changes of FDG metabolism level is helpful to objectively evaluate the effect of chemotherapy on brain function.TLG,clinical stage and chemotherapy cycle have nothing to do with the brain FDG metabolism induced by chemotherapy,but the date between PET/CT and off chemotherapy may be related to the changes of brain FDG metabolism induced by chemotherapy.