FDG PET/CT imaging characteristics in multiple myeloma patients at staging and follow-up

Learning Objectives On FDG PET/CT imaging, 1. Identify different patterns of the disease presentation at staging. 2. Recognize findings for recurrence and post-therapy presentations. 3. Understand and identify the potential pitfalls.

Multiple myeloma (MM) is a plasma-cell malignancy, characterized by osteolytic lesions causing pathological fractures, cord compression and hypercalcemia. Depending on M-protein and plasma cell levels, disease spectrum varies from monoclonal gammopathy of undetermined significance (MGUS) to symptomatic MM. The bone lesions rarely heal even in complete remission. Sensitive imaging techniques are essential in the diagnosis, staging and restaging of MM. The Durie/Salmon-plus staging system incorporated FDG-PET or MRI information;focal lesion number, extent of bone marrow disease. The pattern of MM infiltration may be focal, multifocal or diffuse on FDG PET/CT. PET/CT is also helpful in detection of extramedullary MM. MM treatment protocol includes induction therapy followed by autologous stem cell transplantation (ASCT). The residual FDG activity after induction before ASCT portends a poor prognosis, prompting treatment changes. The detection of impending vertebral collapse, sequelae of prior fractures, detection of active MM in small lytic areas, differentiation of bone healing or arthritic changes from active MM, extramedullary MM or soft tissue components and infection is of crucial clinical value for management decisions. Bone marrow stimulation have PET characteristics similar to that of diffuse marrow infiltration posing a potential pitfall. In light of the increasing use of FDG PET/CT for MM staging and treatment monitoring, it is important to be familiarized with imaging findings and interpretative pitfalls to avoid false readings at both staging and restaging. This presentation will review most relevant PET/CT findings for MM by disease stage, treatment related findings, recurrence patterns and potential diagnostic pitfalls