Study Compares MRI And PET-CT Scans For Evaluation Of Multiple Myeloma
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 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 (abstract).
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The problem with PET/CT is that it subjects you to a LOT of radiation. Far, far more than a cat scan, which is already way too much.
Unless you have a very strong need for PET/CT, I would advise MRI with STIR exclusively.
Frank Heasley, Ph.D.
Bacteriology, UC Berkeley 1978 (retired)
dx 09/23/07 at 60y/o
Please remember that anything I post is written from my personal perspective and experiences only, and should not be taken as a recommendation. Any changes or additions to your therapeutic regimen should always be discussed with your physician first. You have my permission to print anything I have written and show it to your physician or oncologist. If you do, I would appreciate hearing about their comments.
I completely AGREE about amount of radiation!!
Would prefer MRI!!
However...the study concludes:
"MRI achieved better results than PET-CT in the staging and in patients with multiple myeloma recurrence. PET-CT, showed prompt change of imaging findings, faster than MRI, in patients with positive response to therapy."
What does this mean? What is 'prompt change"?...
Does this mean, when on therapy, PET gives best response...but what is best for ongoing subsequent evaluation?
This studies, conclusion seems to say, that initially 4 staging MRI is better than PET but subsequent to that it is not superior to PET, is that correct?
IOW's if you have achieved a CR...MRI is NOT superior to PET?
Which begs the question...what should a patient choose for maintenance, PET or MRI as ongoing evaluation?
I get MRI is better for newly diagnosed, but which will detect disease relapse best?
Oh... OK...I think I get it...while a patient is on therapy...a PET will show those changes from therapy best..in real time.
But once a patient is in CR..the MRI will detect 'new disease relapse" best? Am I understanding this correctly.
Sorry for so many posts..but I think, many patients may be as confounded as me.
As I read it now, if I am being diagnosed, MRI is best..if I am looking for changes DURING therapy, PET is the first choice to show therapeutic efficacy. ONCE I reach CR..then I want to go to MRI as the ongoing test to detect new relapse?
Hmmmm, still thinking on this...I think what the study is truly saying is the difference in how the tests detect disease. PET..needs active disease which will take up FDG...but if your disease is in remission then it will not uptake the FDG which PET illuminates?
So what we are actually noting is the differnce in how the tests work. MRI does not rely on metabolically active disease for disease, so it will highlight lesions INDEPENDENT of metabolic activity, which PET relies on?
Which means we are illuminating the variance in how each test detects? i.e. you must have active disease that will uptake the FDG, if you are showing disease that may not be metabolically active enough for FDG, it will not show, but MRI will still detect that?
Sorry, for thinking outloud...but the difference in the tests seems to be dependent on HOW each test detects sensitivity, I think?
You HAVE to have metabolically active disease for PET but MRI picks up disease independent of the metabolism essential for FDG uptake?
Hi suzierose, this interpretation is correct:
"As I read it now, if I am being diagnosed, MRI is best..if I am looking for changes DURING therapy, PET is the first choice to show therapeutic efficacy. ONCE I reach CR..then I want to go to MRI as the ongoing test to detect new relapse?"
The reason why PET-CT is more accurate for detecting remission is, as you described, based on differences in the way the two techniques work.
MRI detects bone lesions, but bone lesions are slow to heal, even if myeloma therapy is working. Therefore, it takes longer for remission to be detected by MRI.
Whereas, PET-CT shows metabolically active disease through the uptake of FDG. When a patient is in remission, there aren't metabolically active cancer cells to take up the FDG, and cancer is not detected on the PET-CT scan.
Therefore, remission is detected more rapidly with PET-CT than MRI.
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