Global and regional brain glucose metabolism decline after systemic chemotherapy

Dear Sir, In recent years, few studies have shown the ability of F-fluorodeoxyglucose positron emission tomography (FDG PET) imaging along with standard semiquantitative measurement indices [e.g., standardized uptake value (SUVmean and SUVmax)] in detecting decreased cerebral function following chemotherapy [1]. Although the life expectancy of patients with cancer has improved with modern chemotherapeutic agents, the adverse effects of such therapies on brain function have become the focus of research in recent years [2]. The results from Horky et al. show a significant decrease of cerebral glucose metabolism post-chemotherapy. The authors analyzed longitudinal FDG PET images of patients with non-central nervous system (CNS) cancers, before and after systemic chemotherapy. They placed a region of interest (ROI) around target areas in coregistered MRI/ PET images and measured the activity of each brain structure in a single transverse slice of that specific structure. Regional semiquantitative indices showed decreased glucose metabolic function in almost all brain areas (SUVmax declines vary from 9 to 24 % and SUVmean declines vary from 6 to 26 % in different areas). Comparing baseline to posttreatment images, they found a mean overall decrease of 22 % (SUVmean) in glucose metabolism in the gray matter and also significant reduction of metabolism in the white matter and germinal zones [3]. The methodology adopted and the data generated by Horky et al. are informative and interesting, especially the observation that a decline in brain function occurs in the entire brain in these patients (Fig. 1) [3]. In line with these findings in a recent paper by Sorokin et al. [4], we reported a significant decline in global brain function as measured by the degree of FDG uptake following chemotherapy. The authors used the imaging software ROVER® (ABX, Hamburg, Germany) for whole cortex quantification. ROVER provides one sole number for the global activity, as a result of default algorithms combining volumetric and metabolic information (Fig. 2). Hence, a total glycolysis assessment is provided, done in an easy and solid fashion. Sorokin et al. analyzed preand post-chemotherapy FDG PET brain images in a selected group of non-CNS cancer patients and found a decrease of 16.9±5.04 % in global cortical metabolism after chemotherapy. In addition to assessing global cortical function with this technique, our group has explored the role of this technique in measuring metabolic activity of subcortical structures (i.e., basal ganglia) and cerebellum in patients with memory loss and dementia [5]. Therefore, we believe methods for quantitatively measuring the whole cerebral cortex, as one functional unit, in addition to regional analysis, will succeed as a way for exploring and heightening our understanding of brain functionality and biology. S. Gholami :A. Alavi (*) Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA e-mail: abass.alavi@uphs.upenn.edu