[Association of tumor metabolic parameters on amino acid PET/CT with EGFR expression]

According to the 2021 WHO classification, molecular-genetic profiling of CNS tumors is the standard for diagnosis. Beyond IDH mutation status, EGFR receptor alterations are significant factors associated with unfavorable prognosis and treatment resistance. Identifying correlations between genetic abnormalities and amino acid PET/CT parameters is important for discovering non-invasive surrogate markers of aggressive phenotype.

To analyze the relationship between EGFR / EGFRvIII gene expression and metabolic PET/CT parameters in patients with glial tumors.

The study included 71 adults with gliomas: glioblastoma (n=52), Grade 3 astrocytoma (n=11), and Grade 3 oligodendroglioma (n=8). All patients underwent PET/CT with ¹¹C-MET (n=41) or ¹⁸F-FET (n=30). The tumor-to-background ratio (TBR) and metabolic tumor volume (MTV) were calculated using a TBR segmentation threshold of 1.6. EGFR / EGFRvIII expression was determined via RT-PCR.

EGFR expression was significantly higher in glioblastomas compared to astrocytomas and oligodendrogliomas. A significant positive correlation was found between EGFR and MTV (Rs=0.44, p=0.02). In patients with astrocytomas, there was a moderate negative correlation between TBR and EGFR expression (Rs=-0.64, p=0.04). No significant correlations were observed in glioblastomas and oligodendrogliomas that may be attributed to high variability of EGFR. EGFRvIII was expressed in 25% of gliomas (exclusively glioblastomas). However, we found no association with metabolic parameters (possibly due to small sample size).

Differences in EGFR expression patterns across various glioma types were demonstrated. Correlation between EGFR gene expression and tumor metabolic volume suggests potential role for PET/CT parameters as prognostic markers.