Reactive bone marrow [18F]FDG uptake after G-CSF and anti-tumour therapy in neuroblastoma: guidance for PET scheduling

Purpose Altered bone marrow [ 18 F]FDG uptake is frequently observed after granulocyte colony-stimulating factors (G-CSF) or anti-tumour treatment but has not been systematically analysed in paediatric neuroblastoma. This study evaluated the relationship between haematopoietic activity and bone marrow [ 18 F]FDG uptake in neuroblastoma patients, and its variation with time since anti-tumour treatment. Methods A single-centre retrospective cohort study was conducted using [ 18 F]FDG PET/CT scans from neuroblastoma patients. Clinical data were extracted from electronic patient records, including G-CSF and anti-tumour treatment and the interval between treatment and imaging. Mean lean body mass–corrected standardised uptake values (SUV) were extracted from the L4 vertebra, liver, and spleen. Laboratory blood values (haemoglobin, haematocrit, thrombocyte, leucocyte, neutrophil), measured within 7 days prior to each scan, were analysed for correlation with SUV. Patients after anti-tumour treatment were stratified by G-CSF status to account for potential effects on haematopoiesis and SUV. Results A total of 126 scans from 37 patients (median age 3.00 years, IQR 1.60 – 6.00) were included. In patients after anti-tumour treatment, bone marrow SUV showed significant negative correlation with haemoglobin (ρ = −0.45), haematocrit (ρ = −0.41) and thrombocytes (ρ = −0.25), and positive with leukocytes (ρ = 0.22), and neutrophils (ρ = 0.26). SUV was significantly higher in anaemic and thrombocytopenic patients, and lower in leukopenic patients. SUV peaked at 8–14 days after anti-tumour treatment ( P < 0.001). Stratification based on treatment with G-CSF showed higher median SUV in G–CSF–treated patients ( P < 0.001). Conclusion Bone marrow [ 18 F]FDG uptake in neuroblastoma patients is enhanced after administration of G-CSF and anti-tumour treatment, reflecting haematopoietic recovery and potentially mimicking metastatic disease. Therefore, based on our findings, we recommend scheduling [ 18 F]FDG PET imaging at least 21 days after the last administration of G-CSF or systemic anti-tumour treatment to avoid misinterpretation of reactive marrow uptake.