Nuclear medicine imaging of multiple myeloma, particularly in the relapsed setting

Multiple myeloma (MM) is characterized by a monoclonal plasma cell population in the bone marrow. Lytic lesions occur in up to 90 % of patients. For many years, whole-body X-ray (WBX) was the method of choice for detecting skeleton abnormalities. However, the value of WBX in relapsing disease is limited because lesions persist post-treatment, which restricts the capacity to distinguish between old, inactive skeletal lesions and new, active ones. Therefore, alternative techniques are necessary to visualize disease activity. Modern imaging techniques such as magnetic resonance imaging, positron emission tomography and computed tomography offer superior detection of myeloma bone disease and extramedullary manifestations. In particular, the properties of nuclear imaging enable the identification of disease activity by directly targeting the specific cellular properties of malignant plasma cells. In this review, an overview is provided of the effectiveness of radiopharmaceuticals that target metabolism, surface receptors and angiogenesis. The available literature data for commonly used nuclear imaging tracers, the promising first results of new tracers, and our pilot work indicate that a number of these radiopharmaceutical applications can be used effectively for staging and response monitoring of relapsing MM patients. Moreover, some tracers can potentially be used for radio immunotherapy.