Relationships of 18F-FDG PET with tumor microenvironment immunotypes, especially PD-L1 and CD15 expression, and prognosis in oral squamous cell carcinoma

Abstract

BackgroundThe relationship between 2-[18F]-fluoro-2-deoxy-d-glucose–positron emission tomography (FDG-PET) findings and programmed death ligand-1 (PD-L1) expression has been reported in several cancers. We investigated the correlations of FDG uptake with immune cell counts, including myeloid-derived suppressor cells (MDSCs), and PD-L1 expression in the tumor microenvironment. We examined 72 patients with oral squamous cell carcinoma (OSCC) with immunohistochemistry data for PD-L1, CD8, S100A8, CD15, and CD33. We used the maximum standardized uptake value (SUVmax) to reflect FDG uptake in each patient.ResultsHigh SUVmax and high MDSC counts were associated with poor prognosis. Significantly higher SUVmax was found in patients with high PD-L1 expression and in those with a high CD15+ cell density (P = 0.03 and P = 0.02, respectively). In multiple regression analysis, the tumor size had the greatest effect on SUVmax (P < 0.001), followed by PD-L1 (P = 0.014), and when the tumor size was excluded, CD15 (P = 0.02) was included in the prediction equation. FDG uptake in some cold tumor subgroups, low PD-L1 expression, and a low CD8+ cell density was linked to significantly lower SUVmax than the other variables. High SUVmax was clearly associated with high PD-L1 expression and/or a high CD15+ cell density.ConclusionsFDG uptake was affected by PD-L1 expression and the density of CD15+ cells in cancer tissue. FDG-PET may illuminate the tumor microenvironment immunotypes before biopsy or resection.