Characterizing bone marrow involvement in Hodgkin's lymphoma by FDG-PET/CT

Fluoro-deoxyglucose positron emmission tomography combined with computed tomography (FDG-PET/CT) is superior to iliac bone marrow biopsy (iBMB) for detection of bone marrow involvement (BMI) in staging of Hodgkin's lymphoma (HL). The present study aims to characterize the patterns and distribution of BMI in HL as determined by FDG-PET/CT.

Reports of FDG-PET/CT studies performed for staging of HL were reviewed. BMI was defined as positive iBMB and/or foci of pathological FDG uptake in the skeleton that behaved in concordance with other sites of lymphoma in studies following chemotherapy. Number of FDG uptake foci, their specific location in the skeleton and the presence of corresponding lesions in the CT component of the study, and stage according to the Ann Arbor staging system, were recorded.

The study included 473 patients. iBMB was performed in 336 patients. Nine patients had positive iBMB (9/336, 3%). Seventy-three patients (73/473, 15%) had FDG-PET/CT-defined BMI. The BM was the only extranodal site of HL in 52/473 patients (11 %). Forty-five patients had three or more foci of pathological skeletal FDG uptake (45/73, 62 %). Sixty-four patients (64/73, 88%) had at least one uptake focus in the pelvis or vertebrae. In 60 patients (60/73, 82%), the number of skeletal FDG uptake foci without corresponding CT lesions was equal to or higher than the number of foci with morphological abnormalities.

FDG-PET/CT demonstrated BMI in 15% of patients with newly diagnosed HL. Diagnosis of BMI in HL by FDG-PET/CT was more sensitive than iBMB with potential upstage in 11% of patients. The most common pattern of FDG-PET/CT BMI was multifocal (at least three foci) skeletal FDG uptake, with at least one focus in the pelvis or vertebrae and no corresponding CT lesions.