Neuroendocrine (NE) lung
tumors are subdivided into the following types; typical (TC) and atypical
carcinoids (AC), large cell neuroendocrine
carcinoma (LCNEC), and
small cell lung carcinoma (SCLC). Moreover, the determinants of the FDG uptakes of NE lung
tumors have not been elucidated. Thus, the aim of the present study was to investigate the relationships between FDG uptake and
glucose transporter type 1 (Glut-1) expression in these NE
tumors. Tissue-proven NE lung
tumor patients (n=32; age, mean+/-S.D.=67.8+/-10 years; male:female=28:4) who had undergone F-18 FDG-PET before treatment were enrolled in this study. There were 1 TC, 3 AC, 5 LCNEC, and 23 SCLC patients. FDG uptakes were quantified using maximum standardized uptake values (maxSUV).
Paraffin sections of
tumor tissues were immunostained using anti-Glut-1 antibody (Neomarkers, 1:50). Levels of Glut-1 expression are presented as percentages of
tumor cells positively immunostained (%Glut-1). Relations between FDG uptakes and Glut-1 expression were assessed using Pearson correlation analysis. The maxSUVs of all NE lung
tumors ranged from 0.6 to 29.5 (mean+/-S.D.=7.7+/-5.4) and %Glut-1 expression ranged from 0 to 100% (18+/-24%). The maxSUVs of all NE lung
tumors were found to be significantly correlated with %Glut-1 expression (r=0.6471, p=0.0001). By subgroup analysis, maxSUV was also found to be significantly correlated with %Glut-1 expression in SCLC (n=23, r=0.6189, p=0.0016). FDG uptake was found to be highly correlated with Glut-1 expression in NE lung
tumors. This result suggests that Glut-1 plays a crucial role in determining FDG uptake in these
tumors.