Potential in MRI and PET-CT Lymphoma Cancer Characterization

“MRI gives us more information and is probably the most important imaging technique in assessing disease activity in myeloma,” said Dr. Jens Hillengass, a physician scientist from the German Cancer Research Center (Heidelberg, Germany) who presented his findings on March 9, 2013, during the State of the Art symposium at the European Congress of Radiology (ECR), held in Vienna (Austria).

Current guidelines for the evaluation of therapy response are chiefly based on serologic markers and reference imaging to track large soft-tissue tumors. However, Dr. Hillengass thinks that imaging, and in particular MRI and PET, should be included in the recommendations, at least in some patients. For instance, many myeloma patients show changes on MRI that are not visible on a skeletal survey. MRI helps to differentiate between bone and bone marrow; it also has higher sensitivity for imaging of bone marrow effects in total, and demonstrates the first infiltration of plasma cells before overstimulation of osteoclasts and the resulting bone destruction.

Recent research indicates that some patients show diffuse infiltration of bone marrow with malignant plasma cells while others show focal infiltration. Several studies have looked at the prognostic significance of findings from MRI and PET, and suggest that a higher number of focal lesions are associated with a worse prognosis, Dr. Hillengass explained. His research group found that if focal lesions in bone marrow disappear upon MRI, then the patient outcome is better than if remission is defined according to serological markers. Being able to show that lesions are still there could help indicate relapse, which is the case for most patients.

If additional indications suggest that MRI can be used to evaluate disease activity and the extent of bone marrow infiltration with plasma cells prior to bone destruction, there might be a stronger case for earlier treatment, before bone destruction has started, Dr. Hillengass believes. “There are good data to say that if lesions persist, then treatment should continue; these data are on high-risk disease based on cytogenetics, and suggest treating patients for a long time is beneficial,” he said.

Interim PET could be used to monitor response-adapted therapy in Hodgkin lymphoma and aggressive non-Hodgkin lymphoma, according to Dr. Sally Barrington, a consultant physician in nuclear medicine at London’s St. Thomas’ PET Imaging Center (UK), who also spoke during the symposium.

PET was added to new response criteria for lymphoma in 2007 for assessment of the end of treatment response. Adding PET to CT response criteria improved the accuracy of measurement of treatment response after chemotherapy, but earlier assessment of response is needed during the course of therapy to improve patient outcome, she explained. “After only one to two cycles of chemotherapy, interim PET can accurately predict response by monitoring the reduction in FDG [fluorodeoxyglucose] uptake, even before there is a change in tumor size,” said Dr. Barrington, who made her point by presenting the five-point scale (5-PS), also called the Deauville criteria, which has been used in trials to score response on early PET scans.

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German Cancer Research Center