Up to 90 percent of multiple myeloma patients develop bone lesions. Lesions form when cells responsible for bone formation are either suppressed or absent and cells responsible for reabsorbing bone are overactive.
Multiple myeloma patients can experience bone destruction in any type of bone. Almost half of the patients suffer bone lesions in the spine; around one third are affected in the skull, pelvis, and ribs; and under one quarter are affected in the humeri, femora, and mandible.
Bone imaging is an important diagnostic procedure used to monitor bone disease in myeloma patients.
Metastatic bone surveys have been the standard method of imaging bones in patients with myeloma. An adequate x-ray (radiograph) will look at the skull, vertebral column, pelvis, and extremities, since these bones are affected in 80 percent of multiple myeloma patients. However, these radiographs are not sensitive enough to detect bone disease if less than 30 percent of bone has been lost. Furthermore, radiographs do not show a response to therapy.
The limitations of radiographs have led to the use of computerized tomography (CT) scans, magnetic resonance imaging (MRI), and positron emission tomography (PET) scans.
Several trials have been done comparing plain radiographs and MRI. The results show that MRI has greater sensitivity than plain radiographs in detecting bone disease and also provides anatomic and physiologic information about bone marrow.The major issue with MRI is lack of specificity.
CT scans are more sensitive than plain radiographs. They can determine the presence or absence of bone destruction when MRI cannot. However, they are not usually used due to the high levels of radiation exposure.
PET scans have been used to detect metastatic bone lesions in patients with myeloma. Whole-body PET scans are more sensitive than x-rays and other imaging methods; thus, they identify marrow disease earlier.
A combination of PET and CT (PET-CT) was compared to whole body x-rays and MRI. The study shows that PET-CT may be more sensitive than whole-body x-rays for small lesions. PET-CT and MRI appear to be equally effective for detecting bone disease in the spine and pelvis. The disadvantage of PET-CT scanning is that inflammatory lesions from an infection, recent chemotherapy, or fracture can appear as false positives.
Skeletal surveys are useful for the initial diagosis of myeloma patients. However, the British Committee for Standards in Hematology does not recommend skeletal surveys, routine MRI, CT, or PET scanning for routine follow-up in myeloma patients due to their lack of sensitivity and variability.The technology should only be used for follow-up in patients when there is an increased fracture risk or lack of response to therapy.
For more information on myeloma bone disease, see the full article in the American Society of Hematology's 2008 Education Program Book, Hematology, and related Beacon articles on the use of bisphosphonates and novel therapies for the treatment of bone disease.