The results of a recent study show that MRI is more accurate than PET-CT for staging newly diag­nosed multiple myeloma patients and identifying patients with re­lapsed disease.

However, the results also show that PET-CT scans are more useful for eval­u­ating a patient’s response to ther­apy.

The study investigators indicate that their results are similar to those of pre­vi­ous studies that com­pared MRI and PET-CT for diagnosing patients and eval­u­ating response to ther­apy.  They point out, how­ever, that since their study is the first to compare MRI and PET-CT for identifying re­lapsed disease, addi­tional studies are nec­es­sary to con­firm their results.

Based on their findings, the investigators recommend that once patients achieve remission, MRI should be used to detect relapse and that PET-CT is not nec­es­sary at that stage of the disease.

Skeletal images obtained from myeloma patients are essential in the detection, evaluation, and grading of bone lesions. These images allow physicians to choose an appro­pri­ate course of treat­ment and provide an accurate prognosis.

X-rays have been widely used to detect skeletal lesions in myeloma patients, but recent studies have dem­onstrated that MRI and PET-CT scans are more sensitive techniques (see related Beacon ^[1] news).

Magnetic resonance imaging (MRI) is a medical imaging technique used to generate internal images of the body.  It allows physicians to view the bones, organs, and other soft tissue.  Its role in myeloma is to allow physicians to detect bone lesions.

PET-CT combines positron emission tomography (PET) and computerized tomography (CT).

Prior to a PET scan, patients are injected with a radioactive molecule called FDG, which builds up in cancer cells. The scan there­fore detects can­cer­ous areas based on radioactivity levels.

By conducting the PET scan simultaneously with a CT scan, which con­structs a three-dimensional image of the body from a series of x-rays, the location of the cancer cells can be de­ter­mined.

In the current study, Italian researchers com­pared the accuracy of MRI and PET-CT for staging a newly diag­nosed myeloma patient, eval­u­ating a patient’s response to treat­ment, and detecting relapse.

Two onco­logic radiologists retro­spec­tive­ly analyzed 210 MRI and 210 PET-CT scans of 191 myeloma patients with a median age of 62 years. In all patients, both images were taken within 15 days of one another.

Sixty-two patients were eval­u­ated at diag­nosis, 58 patients were eval­u­ated after treat­ment, and 90 were eval­u­ated during follow-up.

In 19 per­cent of the patients imaged at the time of diag­nosis, PET-CT scans and MRI scans falsely indicated an earlier stage of disease com­pared to traditional Durie-Salmon staging.

Specifically, PET-CT scans resulted in the down staging of 18 per­cent of patients, and MRI led to down staging in 2 per­cent of patients.

PET-CT scans detected lesions outside of the MRI field of view in 37 per­cent of newly diag­nosed patients.  The investigators indicated that whole-body MRI may have been able to detect the lesions in these patients.

Of the patients eval­u­ated after treat­ment, 69 per­cent achieved a com­plete response. PET-CT detected response to treat­ment more quickly than MRI.  Specifically, PET-CT showed minimal to no sign of activity in these patients, but MRI still indicated active disease in 68 per­cent of the patients who responded.

Eleven per­cent of patients who were imaged during follow-up re­lapsed during that time. MRI detected active lesions in 80 per­cent of these patients, while PET-CT detected myeloma-related lesions in 50 per­cent of these patients.

For more in­for­ma­tion, please see the study in the European Journal of Radiology ^[2] (abstract).