Bone disease is characteristic of multiple myeloma: 70%–80% of patients present with bone disease at diagnosis. Imaging studies such as X-ray, CT, MRI, and PET are used to assess the status of a patient's bones and/or bone marrow at diagnosis and relapse.
Learn about the uses, benefits, and limitations of the various types of imaging studies.
X-rays are the oldest and least sensitive method to detect myeloma-caused bone damage. A full skeletal X-ray survey can demonstrate loss or thinning of bone (osteoporosis or osteopenia), holes in bone (lytic lesions), and/or fractures. X-rays are simple and quick procedures, are covered by insurance, and are widely available, but their role in the diagnosis of myeloma has been eclipsed by more sensitive studies. X-rays can detect bone damage only after 30% or more of the hard outer bone has been destroyed. Moreover, X-rays cannot distinguish between old bone damage where myeloma is no longer active and sites of active disease
MRI (Magnetic Resonance Imaging)
Magnetic resonance imaging (MRI) is a non-invasive way to produce a detailed two- or three-dimensional image of structures inside the body. It is the preferred study for imaging the spine, pelvis, and sternum, and for detecting focal lesions (early abnormal areas in the bone) in patients with smoldering myeloma. It is useful for imaging plasmacytomas and compression of the spinal cord.
MRI is useful for rapidly detecting new disease, but there is at least a nine-month lag before an MRI will look normal after an area of myeloma has been successfully treated and is no longer active. In addition, MRI may pose a problem for patients who have metal implants. Whole-body MRI is gaining momentum for the assessment of patients with MGUS, SMM, and myeloma, but availability, cost, and standardization of technique remain problematic.
Patients should discuss the use of contrast agent gadolinium with their oncologists prior to scheduling an MRI. In December 2017, the Food and Drug Administration (FDA) required "a new class warning and other safety measures for all gadolinium-based contrast agents (GBCAs) for magnetic resonance imaging (MRI) concerning gadolinium remaining in patients’ bodies, including the brain, for months to years after receiving these drugs," according the FDA's website. Gadolinium contrast is a particular problem for myeloma patients with kidney involvement. It should be possible to use MRI without gadolinium contrast to assess myeloma bone disease.
CT or CAT Scan (Computerized Axial Tomography)
Whole-body low-dose computed tomography (WBLDCT) is the new standard for evaluating myeloma bone disease. Computerized axial tomography (CT or CAT) scan uses X-ray technology to create a three-dimensional digital image of the body that is more precise than X-ray and can provide clear, detailed images of bone lesions.
Positron emission tomography, or PET, requires that a patient be injected with fluoro-deoxyglucose (FDG), a sugar-fluorine compound that is taken up by the body's actively multiplying cells. The areas with the highest concentrations of fluorine "glow," and can indicate actively growing cancer cells.
PET scanning covers the whole body, is very sensitive in detecting potential tumor activity, and is the only "real-time" imaging study. It can detect early changes in the bone marrow before there is destruction of bone. It is a valuable tool when standard blood and urine tests do not provide enough information about potential disease activity, especially so when a patient has non-secretory myeloma (myeloma cells that secrete no monoclonal protein). PET allows an assessment of disease status without the need for a bone marrow biopsy.
PET scans are the only imaging study that includes extramedullary disease, which is myeloma that grows outside the bone marrow. PET scanning is included in the IMWG's consensus statement on assessment of response to treatment. The IMWG states that PET scans are a requirement, along with either Next Generation Flow (NGF) or Next Generation DNA Sequencing (NGS)—both of which analyze tissue from the bone marrow—to assess minimal residual disease. Only PET scans are able to detect areas where myeloma is growing both outside and inside the bone marrow.
PET/CT combines PET and CT scans in sequential studies, allowing the radiologist to perform a CT scan of areas that light up on PET. PET/CT provides information both about past damage and current cancer activity, thus enabling the doctor to study changes over time. It is a highly accurate study used in diagnosis, therapy assessment, and prognosis of myeloma, but is expensive and time-consuming.