Correlation Between (18)F-FDG Uptake and Immune Cell Infiltration in Metastatic Brain Lesions

BACKGROUND: The purpose of this study was to investigate the correlation between (18)F-fluorodeoxyglucose (FDG) uptake and infiltrating immune cells in metastatic brain lesions. METHODS: This retrospective study included 34 patients with metastatic brain lesions who underwent brain (18)F-FDG positron emission tomography (PET)/computed tomography (CT) followed by surgery. (18)F-FDG uptake ratio was calculated by dividing the standardized uptake value (SUV) of the metastatic brain lesion by the contralateral normal white matter uptake value. We investigated the clinicopathological characteristics of the patients and analyzed the correlation between (18)F-FDG uptake and infiltration of various immune cells. In addition, we evaluated immune-expression levels of glucose transporter 1 (GLUT1), hexokinase 2 (HK2), and Ki-67 in metastatic brain lesions. RESULTS: The degree of (18)F-FDG uptake of metastatic brain lesions was not significantly correlated with clinical parameters. There was no significant relationship between the (18)F-FDG uptake and degree of immune cell infiltration in brain metastasis. Furthermore, other markers, such as GLUT1, HK2, and Ki-67, were not correlated with degree of (18)F-FDG uptake. In metastatic brain lesions that originated from breast cancer, a higher degree of (18)F-FDG uptake was observed in those with high expression of CD68. CONCLUSIONS: In metastatic brain lesions, the degree of (18)F-FDG uptake was not significantly associated with infiltration of immune cells. The (18)F-FDG uptake of metastatic brain lesions from breast cancer, however, might be associated with macrophage activity.