Prognostic value of bone marrow and tumor ¹⁸F-FDG uptake on PET/CT in patients with oropharyngeal cancer and the interplay between inflammation and FDG uptake

Aims To examine the prognostic value of F-18 fluorodeoxyglucose (FDG) uptake in the bone marrow (BM) for disease recurrence and survival in patients with oropharyngeal squamous cell carcinoma (OP-SCC). The secondary aims were to evaluate the prognostic value of PET/CT parameters for the primary oropharyngeal tumor and total tumor burden, and to assess the correlation between FDG uptake variables and serum inflammatory markers. Methods This was an observational study of 91 patients with OP-SCC who underwent pretreatment FDG-PET/CT. The patients' blood samples were collected before treatment, and treatment was administered with the intention to cure. The median follow-up time was 40 months. The PET parameters measured were SUVmeanBM for the assessment of BM FDG uptake, SUVmean, SUVmax, total lesion glycolysis (TLG), and metabolic tumor volume (MTV) for the evaluation of primary oropharyngeal tumor and total tumor burden. Blood samples were analyzed to determine each patient's white cell, red cell, and platelet cell counts, hemoglobin, and C-reactive protein level. In a subgroup of 33 patients, blood serum was analyzed to evaluate the expression of serum immune proteins using a proximity extension assay (Olink Proteomics). Methods This was an observational study of 91 patients with OP-SCC who underwent pretreatment FDG-PET/CT. The patients' blood samples were collected before treatment, and treatment was administered with the intention to cure. The median follow-up time was 40 months. The PET parameters measured were SUVmeanBM for the assessment of BM FDG uptake, SUVmean, SUVmax, total lesion glycolysis (TLG), and metabolic tumor volume (MTV) for the evaluation of primary oropharyngeal tumor and total tumor burden. Blood samples were analyzed to determine each patient's white cell, red cell, and platelet cell counts, hemoglobin, and C-reactive protein level. In a subgroup of 33 patients, blood serum was analyzed to evaluate the expression of serum immune proteins using a proximity extension assay (Olink Proteomics). Results The univariate analysis revealed that SUVmeanBM and tumor-specific parameters (SUV(max)tumor, SUV(mean)total, SUV(max)total, MTVtotal, TLGtotal) were significantly associated with recurrence-free survival (RFS). After adjusting for age, sex, and stage only SUVmeanBM remained significantly associated with RFS. Spearman's correlation identified several correlations between PET parameters and inflammatory markers. Conclusions Our results show that several FDG-PET/CT parameters may have a prognostic value of treatment outcome in patients with OP-SCC. However, SUVmeanBM was the only independent PET parameter that showed a prognostic value for RFS in the study cohort. Moreover, the study findings might suggest an association between systemic inflammation and the metabolic activity in the BM.