The effect of prophylactic cranial irradiation on brain 18F-fluorodeoxyglucose uptake in small cell lung cancer in the metabolic imaging era

Abstract

Introduction: Prophylactic cranial irradiation (PCI) increases survival in patients with small-cell lung cancer. Although the underlying pathophysiology is not fully understood, it has been associated with posttreatment neurocognitive impairment. Our study aims to show the brain's glucose metabolism change after PCI with 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT). Materials and Methods: A total of 17 patients who underwent PET/CT before and after PCI were evaluated retrospectively. 18F-FDG PET images of the brain before and after PCI were compared visually and semi-quantitatively using MI-Neurology Software. The brain was automatically segmented into eleven regions by this software. The mean standard uptake values (SUVmean) of all brain regions were measured within the automatically drawn region of interest area, and standard uptake value ratio (SUVR) values were found for each region by taking the brainstem SUVmean value as a reference. SUVR values were calculated from PET/CT scannings taken before and after PCI for each patient. The P < 0.05 value was considered statistically significant in comparisons. Results: We found a significant decrease in 18F-FDG uptake and glucose metabolism of the brain after PCI when compared with PET/CT before PCI in all brain regions identified according to the Combined-AAL atlas (all P < 0.001). Similarly, a significant decrease was found in brain 18F-FDG uptake on PET/CT taken after PCI in the brainstem used to calculate SUVR (P = 0.039). Conclusion: 18F-FDG PET/CT neuroimaging may be a new metabolic imaging technique for diagnosing radiation-induced cognitive impairment in the metabolic imaging era.