Effect of Corticosteroids on 18F-FDG Uptake in Tumor Lesions After Chemotherapy

Effect of Corticosteroids on ¹⁸F-FDG Uptake in Tumor Lesions After Chemotherapy

Lieselot Brepoels¹^,2, Sigrid Stroobants¹^,2, Peter Vandenberghe³, Karoline Spaepen¹, Patrick Dupont¹^,2, Johan Nuyts¹^,2, Guy Bormans²^,4, Luc Mortelmans¹^,2, Gregor Verhoef⁵ and Christiane De Wolf-Peeters⁶

¹ Department of Nuclear Medicine, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium; ² Molecular Small Animal Imaging Center, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium; ³ Center of Human Genetics, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium; ⁴ Laboratory for Radiopharmacy, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium; ⁵ Department of Hematology, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium; and ⁶ Department of Pathology, University Hospital Gasthuisberg and Catholic University Leuven, Leuven, Belgium

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FIGURE 1. Evolution of viable tumor cells (A) and stromal mouse cells (B) as measured by flow cytometry in mice treated with chemotherapy ( ${blacksquare}$ , group A) and mice treated with chemotherapy and hydrocortisone ( ${square}$ , group B) and expressed as mean percentage ± SEM. x-axis: different time points (days after treatment); y-axis: percentage cell fraction out of total, as measured by flow cytometry. *Significant differences after Bonferroni correction between both treatment groups.

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FIGURE 2. (A) Serial small-animal PET images in the same mouse on D0 (before chemotherapy) and on D+6, D+9, D+13, and D+16 after treatment. (B) Evolution in SUV_mean, SUV_max, Vol_metab, and TLG as measured by serial small-animal PET scanning in mice treated with chemotherapy ( ${blacksquare}$ , group A; n = 5) compared with mice treated with chemotherapy and hydrocortisone ( ${square}$ , group B; n = 5) and expressed as mean ± SEM. *Significant at P $≤$ 0.05 level by unpaired Student t test.

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FIGURE 3. Histopathologic sections on D0 (before treatment) and on D+9 after treatment after staining with hematoxylin and eosin (H&E) and immunostaining with anti-CD20 and Ki67. (A) Histology on D0 shows high density of CD20-positive tumor cells, with high proliferation rate. (B) D+9 in group A: diffuse stromal reaction of primarily mononuclear cells. (C) D+9 in group B: influx of primarily granulocytes.

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FIGURE 4. Subdivision of inflammatory reaction in NK cells (NK1.1), granulocytes (Ly6G (Gr-1)), and macrophages (F4/80) as measured by flow cytometry and expressed as percentage of total stromal host cells over time (2 mice per time point) in group A (A) and group B (B).