Diffusely Increased Bone Marrow 18F-FDG Uptake Is an Independent Predictor of Focal Bone Lesions in Patients with Newly Diagnosed Classical Hodgkin Lymphoma

Background: 18F-FDG PET/CT is recommended in the initial staging of patients with classical Hodgkin lymphoma (cHL). Whereas focal 18F-FDG uptake in the skeleton is considered to represent bone involvement, it is still unclear whether diffusely increased 18F-FDG bone marrow uptake (BMU) indicates lymphoma infiltration or merely reflects a state of general inflammation. This retrospective study was therefore performed to study the relationship between pre-therapeutic (PET0) 18F-FDG BMU and the presence of focal bone lesions.

Methods: A total of 139 patients (median age 44, range 8-83) referred to PET/CT between 2008 and 2014 for HL staging were included. All PET0 and post-therapeutic (PET2) images were reviewed and evidence of focal bone lesions was recorded (unifocal: ≤2 lesions, multifocal: >2 lesions). In addition, 18F-FDG uptake (SUVmax) was semiquantitatively measured in the vertebral bone marrow (SUVvertebra) and in the right lobe of the liver (SUVliver). BMU was calculated as SUVvertebra/SUVliver. The relationship between focal bone lesions on PET0 and BMU as well as age was subsequently analysed by logistic regression.

Results: In total 30/139 (22 %) patients had focal bone lesions at initial staging (10 unifocal, 20 multifocal). BMU at initial presentation was generally increased in all patients when compared with the post-therapeutic PET/CT (PET0: 1.22 +/- 0.03 vs. PET2: 0.95 +/- 0.03, p<0.001). In a logistic regression model diffusely increased BMU at PET0 (p=0.01) as well as age (p=0.01) were both independent predictors of focal bone lesions.

Conclusion: Diffusely increased 18F-FDG uptake is an independent predictor of skeletal bone lesions in patients with HL. Evidence of increased BMU might be evaluated as an additional outcome predictor in the pre-therapeutic risk assessment of patients with HL. With the purpose of validating these findings, we will analyze an independent cohort of Swedish cHL patients and joined data from both cohorts will be presented at the meeting.