SLC2A1 and cancer: Unlike most malignant tumors, the use of FDG in RCC is of limited value for several reasons: (1) FDG is excreted by the kidney, which leads to a low tumor background ratio; (2) downregulation of glucose transporter 1 (GLUT1) expression leads to low FDG-avidity; (3) Different RCC subtypes have different FDG-avidity.