In multiple myeloma, skeletal radiographs are still regarded as the reference imaging examination because they help to establish the stage of the disease according to the Durie-Salmon Staging System. Whole-body MRI using T1 and STIR sequences increases the detection of myeloma lesions. MRI-measured diffusion has demonstrated high sensitivity in terms of detection in oncology. The main objective of this study is to compare conventional radiographic staging with an MRI whole-body diffusion technique (called DWIBS) in detecting bone lesion monoclonal plasma cell pathologies (multiple myeloma, plasma cell leukaemia, plasmacytoma and MGUS).

Twenty-seven patients were included (multiple myeloma: 24; plasma cell leukaemia, MGUS and plasmacytoma: 1 each). All of them had a whole-body MRI diffusion examination (using a DWIBS sequence). Diffusion MRI and conventional radiographs were compared according to the Durie-Salmon Staging System. In case of doubtful lesions, 12 months of monitoring was used as the reference method for the definitive diagnosis.

The overall concordance rate between the two techniques was 63%. The DWIBS sequence detected a higher number of lesions leading to a higher Durie-Salmon stage in 37% of the patients: one stage I to II, seven stage I to III, and two stage II to III. In 18.5% of the patients, the MRI was positive while the radiographs were normal and these discrepancies were most often located in sites poorly explored by X-ray (spine, pelvis and ribs). In one patient (4%), the MRI provided a stage lower than that of the X-rays (stage II vs. III). In this case, the X-rays were positive at the humerus and femur, unlike the DWIBS sequence. Our per site analysis confirmed the clear superiority of the DWIBS sequence when compared with X-rays in the exploration of the cervical spine (56 vs. 0%, P<0.001), dorsal spine (81vs. 31%,P<0.0002), lumbar spine (70 vs. 35%, P<0.0124), pelvis (81 vs. 33%, P<0.0005) and ribs (74 vs. 36%, P<0.0009).

The DWIBS MRI leads to an increase in the final Durie-Salmon stage. Although its place in the preoperative treatment of multiple myeloma still has to be assessed, this study suggests its potential interest.