Biological correlation of ¹⁸F-FDG uptake on PET in pulmonary neuroendocrine tumors

It is widely recognized that pulmonary neuroendocrine tumors (PNET) include a spectrum that ranges from low-grade typical carcinoid (TC) and atypical carcinoid (AC) to high-grade large cell neuroendocrine carcinoma (LCNEC) and small cell lung carcinoma (SCLC). However, little is known about the usefulness of 2-[(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG) positron-emission tomography (PET) in such tumors. We therefore, conducted a study including the analysis of the underlying biology of (18)F-FDG uptake.

Thirty-four patients with early-stage PNETs who underwent (18)F-FDG PET before treatment were included in this study. Tumor sections were stained by immunohistochemistry for glucose transporter-1 (Glut1 and Glut3), hypoxia-inducible factor-1 alpha (HIF-1α), hexokinase-I, vascular endothelial growth factor (VEGF), microvessel density (MVD) determined by CD34 and (Akt)/mammalian target of rapamycin (mTOR) signaling pathway.

(18)F-FDG uptake correlated significantly with Glut1, HIF-1α, VEGF and CD34 expression. Uptake of (18)F-FDG tended to increase from low-grade to high-grade PNETs. Tumor metabolic activity was a useful marker for predicting postoperative prognosis in patients with early-stage PNETs.

The amount of (18)F-FDG uptake is determined by the presence of glucose metabolism, hypoxia and angiogenesis.