December 14, 2005 -- Fluorodeoxyglucose positron emission tomography (FDG-PET) may serve as an important addition to standard computed tomography (CT) imaging in determining whether or not patients with lymphoma who have relapsed should progress to autologous stem cell transplantation.

Investigators presented the findings on the benefits of FDG-PET here on December 11^th at the annual meeting of the American Society of Hematology (ASH).

"Among relapsed lymphoma patients who then have a positive PET scan and who then go through autologous stem cell transplantation, the transplantation outcome is often very poor," said Jakub Svoboda, MD, third year fellow, University of Pennsylvania, Philadelphia, Pennsylvania, United States.

"Most centers just use CT scans to assess patients' response to the chemotherapy," Dr. Svoboda added. "But if you add the PET scan, it can help guide clinicians in deciding whether or not the patient should receive transplantation. If the PET scan is positive, then the chance of the transplant having any meaningful clinical impact is low."

For this retrospective analysis, Dr. Svoboda and his colleagues reviewed data on 19 patients with diffuse large B-cell lymphoma and 18 with Hodgkin's lymphoma, four with mantle cell, three with follicular and three with other lymphomas. All patients had an FDG-PET scan after at least two cycles of salvage chemotherapy in advance of their autologous stem cell transplant.

The researchers excluded three patients from the analysis because their FDG-PET scan results were inconclusive. Researchers then categorized 26 patients into FDG-PET scan negative and 18 scan positive. Both groups were evaluated for event-free survival, defined as the interval between the date of the transplant to the date of relapse after complete remission, the date of progression for patients without complete remission, or the date of death from any cause in the absence of relapse.

The researchers noted no statistically significant differences in the distribution of lymphoma subtypes between the two groups.

Results show that the median event-free-survival rate in the FDG-PET negative group was 18 months (range 3-58), with 14 patients (54%) remaining in complete remission.

However, among the patients in the FDG-PET positive group, the median event-free survival rate was 5 months (range 1.5-19), with one patient (6%) remaining in complete remission.

The researchers said that more research is needed to confirm these findings. "From what we have seen, however, patients should probably have both a CT scan and a FDG-PET scan prior to receiving a transplant," Dr. Svoboda said.