Analysis of FDG PET Diffuse Bone Marrow Uptake in Staging of Hodgkin’s Disease: A Reflect of Disease Infiltration or Just Inflammation?.

FDG-PET has been successfully evaluated in the management of Hodgkin’s lymphoma (HL) and the most recent international guidelines recommended FDG-PET for initial staging and final therapeutic assessment. However, FDG PET diffuse bone marrow uptake (BMU) is frequently observed and remains difficult to analyse. The aim of this study was to evaluate the correlation between bone marrow involvement and BMU in HD. Methods: 106 HD patients (median age was 31 years range from 9 to 81; male gender in 23 cases) who underwent FDG PET/CT were retrospectively analysis. BMU level was graduated according to liver uptake. In addition, as semi-quantitative reference SUVmax was assessed upon sacral promontory. These data were compared with patient characteristics including age, Ann Arbor staging, bulky disease (Tumor burden > 10 cm), presence of B symptoms, bone foci on PET (n=106), bone marrow biopsy (n=75), leukocyte count (n=74), LDH (n=87) and inflammatory parameters measured in the serum (C-Reactive Protein (CRP) (n=83) and fibrinogen (n=60)). Univariate and multivariate analysis were performed. A Fisher’s exact test and a Kruskal-Wallis equality of population rank test were used to analyse qualitative and quantitative parameters, respectively. Results: No statistical link was found between BMU and stage, bulky disease, bone marrow involvement (BMI), bone foci on PET or LDH. In contrast, univariate analysis showed correlation between BMU and age (p =0.0001), B symptoms (p =0.028 for clinical), CRP (p=0.0001), fibrinogen (p=0.0111) and leukocyte (p=0.0024). Multivariate parameters analysis found independent correlation between BMU and CRP level (p<0.0001). Sacrum SUV was correlated with inflammatory parameters as BMU and with disease extension parameters like stage (p=0.0001), BMI on biopsy (p=0.0127) and bone foci on PET (p=0.0498). No BMI was found in patients presented with SUVmax below 3.5. Conclusion: This study demonstrates that the intensity of FDG-PET bone marrow uptake in HD is not correlated to BMI but related to inflammatory parameters probably reflecting the cellular activation within the BM. Semi-quantitative analysis of SUV could be useful to improve bone uptake interpretation because no infiltration is found under a SUV level.