Myeloma bone and extra-medullary disease: Role of PET/CT and other whole-body imaging techniques

Multiple myeloma (MM) is the second most common hematological malignancy. Although it can affect different organs, the bone compartment stands out both in terms of prevalence and clinical impact. Despite the striking advances in MM therapy, bone disease can remarkably affect the patient's quality of life. The occurrence and extension of bone marrow and extra-medullary involvement should be carefully assessed to confirm the diagnosis, to locate and whenever possible prevent dreadful complications such as pathological fractures and spinal cord compression, and to establish suitable therapeutic measures. Many imaging techniques have been proposed for the detection of MM skeletal involvement. With the development of more sophisticated imaging tools, it is time to use the right technique at the right time. Based on the review of the literature and our own experience, this article discusses advantages and disadvantages of the different imaging methods in the work-up of MM patients, with particular emphasis on the role that PET/CT can play. It is emphasized that whole body low-dose computed tomography should be the preferred imaging technique at baseline. However, bone marrow infiltration and extra-medullary manifestations are better detected by whole body magnetic resonance imaging. Positron emission tomography/computed tomography, on the other hand, combines the benefits of the two mentioned imaging procedures and is particularly useful not only for the detection of osteolytic lesions unrevealed by conventional X-ray, but also in the assessment of prognosis and therapeutic response.