Combined PET/CT Scanning Beneficial for Lymphoma Patients

Combined positron emission tomography (PET) and computed tomography (CT) imaging of lymphoma patients is a more effective method to evaluate the response to radiation therapy, and may help patients avoid unnecessary follow-up treatments, according to a recent study.

The findings of the study, performed by researchers at the University of Southern California (USC; Los Angeles), were published in the March 2008 issue of the journal Radiology. The clinical study is the first to show the advantage of combined PET-CT imaging in evaluating radioimmunotherapy for patients with non-Hodgkin lymphoma, according to Gary Ulaner, M.D., Ph.D., radiology resident, and nuclear medicine fellow at the USC Keck School of Medicine and the lead investigator of the study.

"Combined PET-CT imaging is more accurate in defining a complete response to radio-immunotherapy treatment,” remarked Dr. Ulaner. "Specifically, PET-CT is able to correctly label inactive scar masses, which are sometimes mistaken for active cancer when CT is used alone.”

Radioimmunotherapy is a type of radiation treatment that targets cancer cells through antibodies. The therapy causes less harm to healthy cells and typically results in fewer side effects than other cancer treatments, according to Dr. Ulaner. Usually, the treatment has been evaluated by use of CT imaging alone, which uses special X-ray equipment to produce multiple images of the inside of the body.

PET is a type of nuclear medicine imaging that uses very small amounts of radioactive material to diagnose or treat disease and other abnormalities. When PET and CT scans are combined, they can produce a more complete image of the cancer metabolism.

Researchers from the USC Positron Emission Tomography Center evaluated five men and five women ranging in age from 38 to 70 years who underwent PET and CT imaging, both several weeks before and several months after radioimmunotherapy for non-Hodgkin lymphoma. After evaluation of CT images alone, 8 of 10 patients were classified as responders to treatment, and 2 patients were classified as having a complete response to the treatment.

After reevaluating with the fused PET-CT scans, researchers found that two patients who had residual lesions had been misclassified. Both of the patients were free of evident disease, and remained healthy after 18 or more months of follow-up.

"Using this relatively novel hybrid imaging means that some patients will only require a one-day treatment of radioimmunotherapy instead of several rounds of chemotherapy,” stated Peter Conti, M.D, Ph.D., professor of radiology at the Keck School of Medicine. "We will have a more accurate image that will identify the patients who have a complete response to the treatment.”

Dr. Conti is a leading specialist in treatment of non-Hodgkin lymphoma with radioimmunotherapy. "We hope this research will result in PET-CT imaging becoming the standard for evaluating patients after treatment. Greater accuracy will improve how physicians care for lymphoma patients.”


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