The Role of Whole-Body Magnetic Resonance Imaging in the Staging and Follow-Up of Bone Disease in Multiple Myeloma.

Radiographic skeletal survey (RSS) is the standard diagnostic tool for the screening of bone lesions in multiple myeloma (MM) at diagnosis and during the course of disease. Its major limitation is the low sensitivity in detecting minimal bone lesions and in differentiating active from inactive osteolyses. Several studies demonstrated the superiority of magnetic resonance imaging (MRI) over RSS for the detection of spinal and pelvis bone lesions. However, a significant proportion of patients develops bone lesions elsewhere, therefore MRI of spine and pelvis is inadequate for the staging and follow-up of patients. Recently, whole-body MRI (WB-MRI) has been used with promising results for the detection of secondary bone lesions in patients with non-haematological malignancies. The aims of this study were to evaluate the potential role of WB-MRI in the staging and follow-up of MM patients, using RSS as a standard of reference, and to study the correlation of MRI findings with biochemical markers of bone turnover. Characteristics of the 9 patients included in the study were the following: median age 57 years (46–67), 6 males and 3 females; 4 patients were untreated and asymptomatic, and 5 previously treated with chemotherapy. On the same day, all patients underwent RSS and WB-MRI, and blood sampling for serum osteocalcin (OC) as a marker of bone formation, and for carboxyterminal telopeptide of type I collagen (ICTP) as a marker of bone resorption. RSS and WB-MRI were read by two independent radiologists. WB-MRI was performed with a 1.5-T scanner (Magnetom Symphony Maestro Class). The skull, thorax, pelvis, femoral and lower leg bones were imaged in coronal planes, while sagittal images of the spine were acquired. T1-weighted spinecho (SE) and short-tau inversion time inversion recovery (STIR) sequences (TR 2670, TE 101, TI 150) with a maximum field of view of 450 mm and slice thickness of 5 mm were obtained. As reference standard contrast-enhanced MRI was performed in patients with discordant data at RSS and WB-MRI.

RSS was negative in 5 patients, whereas in 4 revealed lytic lesions stable with respect to prior controls. In the group of RSS-negative patients, WB-MRI was positive in 3/5 cases, 2 of whom had marrow and serum progression at the time of evaluation. All 4 RSS-positive patients showed lytic lesions also at WB-MRI with an overlapping pattern of distribution. Only the lesions at humeral bones were not detected by WB-MRI, because humeri are outside the field of view. WB-MRI, however, was superior to RSS in identifying lytic lesions in the spine and pelvis. Biochemical markers of bone metabolism were evaluable in 8/9 cases. ICTP levels were high only in one patient without evidence of bone lesions both at RSS and WB-MRI. OC levels were low in 6 of 8 evaluable patients, and 5 of them had a positive WB-MRI.

In conclusion, WB-MRI seems more sensitive than RSS for the detection of bone lesions in MM patients. In particular, it is more suitable for the initial staging of the disease in asymptomatic stage I MM and for the follow-up of patients with a stable picture of lytic lesions at RSS. There is no correlation between ICTP levels and the radiological findings, whereas OC levels are decreased in patients with extensive bone involvement.