MRI Is Most Sensitive Method for Detecting and Staging Multiple Myeloma

Background
Ten percent of all hematologic malignancies are secondary to multiple myeloma. Detection of skeletal involvement is critical for staging, treatment planning, and prognosis. Myeloma can present with multiple, punched out lytic lesions, but can also be diffusely infiltrating, mimicking osteoporosis.

Prior studies demonstrated radiographs to be false negative in 30% to 70% of cases. The Durie and Salmon PLUS staging system was developed using whole-body MRI. This, however, is not always available and is not always covered by health insurance.

The objective of a recent study was to compare detection rate of bone lesions and to assess accuracy of staging in whole-body MRI and whole-body MDCT.

The study has concluded that whole-body MRI is superior to whole-body MDCT in the detection and staging of multiple myeloma.

Design/Participants
Prospective analysis of 41 patients newly diagnosed with multiple myeloma.

Methodology
All patients had whole-body MDCT, whole-body MRI, and iliac crest biopsies. Both CT and MRI were performed from the skull to the knees.

Results of the Study
On MRI, 15 patients had no involvement, and 26 patients had 975 regions affected. Thirteen patients had focal disease and 13 patients had combined diffuse and focal involvement. Twenty patients had multifocal disease and one patient had only diffuse disease.

On the Durie and Salmon PLUS staging system, 21 patients were stage I, 2 were stage II, and 18 were stage III. On MDCT, 19 patients had no involvement. In 22 patients, 426 regions were affected. Nine patients had multifocal disease. According to the Durie and Salmon PLUS staging system, 25 patients were stage I, 7 were stage II, and 9 were stage III. Concordance was shown in 15 patients with no involvement, and in 4 patients with focal involvement.

In 21 patients, MRI showed more extensive disease than CT. Seven of these patients had a focal pattern, 13 a combined pattern, and 1 patient had a diffuse infiltrative pattern. One patient showed more extensive disease on CT. Four patients were stage I on CT and stage II or III on MRI. Seven patients were stage II on CT, but stage III on MRI. The difference in detection rate was statistically significant (P <0.001).

Conclusions
Whole-body MRI leads to a significantly higher detection rate and staging than whole-body MDCT in patients with multiple myeloma.

Reviewer’s Comments
Whole-body cross-sectional imaging should replace radiographs, ideally with MRI, but if that is not feasible, MDCT should be performed. The radiation dose for a low-dose CT is only slightly more than for a skeletal survey. This is not significant in a tumor patient with limited survival.

Author: Cornelia Wenokor, MD

Reference
Baur-Melnyk A, Buhmann S, et al. Whole-Body MRI Versus Whole-Body MDCT for Staging of Multiple Myeloma. AJR Am J Roentgenol; 2008; 190 (April): 1097-1104.