Correlation of EGFR or KRAS mutation status with (18)F-FDG uptake on PET-CT scan in lung adenocarcinoma

BACKGROUND: (18)F-fluoro-2-deoxy-glucose ((18)F-FDG) positron emission tomography (PET) is a functional imaging modality based on glucose metabolism. The correlation between EGFR or KRAS mutation status and the standardized uptake value (SUV) of (18)F-FDG PET scanning has not been fully elucidated. METHODS: Correlations between EGFR or KRAS mutation status and clinicopathological factors including SUV(max) were statistically analyzed in 734 surgically resected lung adenocarcinoma patients. Molecular causal relationships between EGFR or KRAS mutation status and glucose metabolism were then elucidated in 62 lung adenocarcinomas using cap analysis of gene expression (CAGE), a method to determine and quantify the transcription initiation activities of mRNA across the genome. RESULTS: EGFR and KRAS mutations were detected in 334 (46%) and 83 (11%) of the 734 lung adenocarcinomas, respectively. The remaining 317 (43%) patients had wild-type tumors for both genes. EGFR mutations were more frequent in tumors with lower SUV(max). In contrast, no relationship was noted between KRAS mutation status and SUV(max). CAGE revealed that 4 genes associated with glucose metabolism (GPI, G6PD, PKM2, and GAPDH) and 5 associated with the cell cycle (ANLN, PTTG1, CIT, KPNA2, and CDC25A) were positively correlated with SUV(max), although expression levels were lower in EGFR-mutated than in wild-type tumors. No similar relationships were noted with KRAS mutations. CONCLUSIONS: EGFR-mutated adenocarcinomas are biologically indolent with potentially lower levels of glucose metabolism than wild-type tumors. Several genes associated with glucose metabolism and the cell cycle were specifically down-regulated in EGFR-mutated adenocarcinomas.