The relationship between bone marrow involvement on 18F-FDG PET/CT and bone marrow biopsy in patients with multiple myeloma and other plasma cell neoplasms

Background: Bone marrow biopsy (BMB) plays a crucial role in the diagnosis and assessment of treatment response in patients with multiple myeloma (MM). 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has been shown to be a complimentary measure of marrow involvement in patients with Hodgkin and diffuse large B cell lymphomas. However, only limited information is available on its relationship with BMB in MM. Aim: To assess the association between bone marrow involvement on 18F-FDG PET/CT, and BMB in patients with MM and other plasma cell neoplasms. Setting: Cape Town, South Africa. Methods: Hundred and three patients undergoing 18F-FDG PET/CT and BMB were included. Plasma cell infiltration (PCI) on BMB was compared for three visual patterns of 18F-FDG bone marrow uptake (irregular, diffuse less than or equal to the liver and diffuse greater than liver). Results: Eighty-four patients had diffuse bone marrow uptake. Of these, 25/84 had uptake greater than liver, all having PCI ≥ 60% and a median value of 85%. Of the 84 patients, the 59 patients with uptake less than or equal to liver had PCI 10% in 57.6% (34/59), and ≥ 10% in 42.4% (25/59) with a median value of 8%. Nineteen patients had irregular bone marrow uptake. Of these, 4/19 (21.1%) had PCI of 10% and 15/19 (78.9%) had PCI ≥ 10%, with the median value of 23%. The median percentage of PCI across the three described patterns of FDG uptake was significantly different (p = 0.0001). Conclusion: 18F-fluorodeoxyglucose positron emission tomography/computed tomography might avoid the need of repeat BMB in most of the patients with diffuse and irregular patterns of 18F-FDG uptake.