¹⁸F-FDG PET/CT for assessment of bone marrow activity in patients with myelofibrosis before and after stem cell transplantation

Objectives Myelofibrosis is a hematopoetic stem cell disorder characterized by bone marrow inflammation, marrow fibrosis and potential leukemic transformation. The aim of this study was to evaluate if ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) is able to noninvasively visualize and quantify the extent and activity of bone marrow involvement, and to assess its value for therapy monitoring after stem cell transplantation (SCT).

Methods 30 patients underwent whole-body ¹⁸F-FDG PET/CT before SCT. An additional PET (PET2) was performed at variable time points after SCT if possible. Bone marrow tracer accumulation was evaluated visually and semiquantitatively by measuring SUVs. Bone marrow biopsies and hematological parameters served as the reference standard.

Results Pretreatment ¹⁸F-FDG accumulation was observed in bone marrow and spleen. A varying extent of bone marrow involvement was observed, ranging from mildly increased uptake in the central skeleton to markedly increased uptake in most parts of the skeleton, gradually decreasing over time since diagnosis (r_s = -0.43, p = 0.019). Pretreatment intensity of bone marrow uptake demonstrated an inverse correlation with histopathological grade of bone marrow fibrosis (r_s = -0.37, p = 0.04). PET correctly identified 2 patients with leukemic transformation which demonstrated a markedly inhomogeneous bone marrow signal. 83.3% of patients with complete histo-hematological remission (CR) after SCT became PET-negative, whereas all patients with non-CR remained PET-positive. 8 patients died before PET2. Neither extent nor activity of bone marrow involvement on pretreatment PET were significantly different in these patients (p > 0.05).

Conclusions ¹⁸F-FDG PET/CT can visualize both extent and activity of bone marrow involvement in patients with myelofibrosis. Bone marrow tracer accumulation can be used to identify responders and non-responders to SCT.