Results of a recent German study suggest that PET-CT scans may be more reliable than whole-body MRI in determining the remission status of multiple myeloma patients after stem cell trans­plan­ta­tion.

The investigators conclude that both PET-CT and whole-body MRI provide useful in­for­ma­tion about a patient’s disease status.  However, MRI often incorrectly detects activity in bone lesions that persist after treat­ment.  They there­fore state that PET-CT may be better than MRI for determining remission status.

Similar results were found in a recent Italian study that com­pared PET-CT and MRI for the evaluation of multiple myeloma at dif­fer­en­t stages of the disease.  This study found that MRI was more accurate than PET-CT for staging newly diag­nosed patients and identifying those with recurring disease. However, the study showed that PET-CT was more reliable than MRI for eval­u­ating a patient's response to ther­apy (see related Beacon news).

To follow-up on the results of the current German study, the investigators recommend addi­tional pro­spec­tive­ studies with a larger number of patients. They also suggest eval­u­ating the per­for­mance of PET-MRI for the detection of bone lesions in myeloma patients, which would combine the strengths of both imaging techniques.

Previous studies have shown that both PET-CT and MRI are superior to x-rays for the detection of myeloma-related bone lesions (see related Beacon news).

Currently, a myeloma patient's remission status is based on blood-related mea­sure­ments. The addi­tional in­for­ma­tion provided by newer imaging techniques could be used to guide further treat­ment.

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 accumulates in cancer cells. The scan then detects can­cer­ous areas based on radioactivity levels.

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

Magnetic resonance imaging (MRI) is a medical imaging technique used to generate detailed images of bones, organs, and soft tissue. Images obtained from an MRI allow physicians to detect bone lesions in myeloma patients.

In the current study, German researchers retro­spec­tive­ly com­pared the per­for­mance of PET-CT and whole-body MRI in determining the remission status of myeloma patients after stem cell trans­plan­ta­tion.

Overall, 31 patients who received a stem cell trans­plant were examined with both PET-CT and MRI. The average age of the patients was 55 years, and all patients underwent a standard evaluation to de­ter­mine disease status. This evaluation in­cluded whole blood count; blood levels of protein, beta-2-microglobulin, C-reactive protein, and free light chains; immuno­fix­a­tion analysis; and bone marrow biopsy or aspiration when appro­pri­ate.

The average time in­ter­val be­tween a patient's last stem cell trans­plant and post-transplant imaging was 3.1 years, with a range of 2 months to 11.9 years.

Prior to the PET-CT and MRI scans, 77 per­cent of the patients had received a donor stem cell trans­plant and 23 per­cent had received an au­tol­o­gous stem cell trans­plant.

At the time of imaging, 68 per­cent were in com­plete remission, 16 per­cent had a very good partial response, and 16 per­cent had a partial response, according to standard methods.

PET-CT scans accurately de­ter­mined the remission status of 74 per­cent of the patients, and there was a sig­nif­i­cant correlation be­tween diagnostic results de­ter­mined by PET-CT and standard methods.

However, MRI accurately de­ter­mined the remission status of 52 per­cent of patients, and there was no correlation be­tween the remission statuses obtained from MRI and standard methods.

PET-CT detected a total of 12 lesions in 9 out of the 31 patients. Whole-body MRI, on the other hand, detected 104 lesions in 21 patients. All of the lesions detected by PET-CT were also detected by MRI.

PET-CT incorrectly detected lesions in 14 per­cent of the patients in com­plete remission and failed to detect lesions in 50 per­cent of the patients with a partial or very good partial response.

In comparison, MRI incorrectly detected a total of 63 lesions in 62 per­cent of the patients in com­plete remission and failed to detect lesions in 20 per­cent of the patients with a partial or very good partial response.

For more in­for­ma­tion, please see the study in European Radiology (abstract).