PET Plays a Role in Radioimmunotherapy for NHL

June 18, 2008

June 18, 2008 (New Orleans, Louisiana) — In subsets of patients with non-Hodgkin's lymphoma (NHL), fluorodeoxyglucose (FDG) positron-emission tomography (PET) can be a valuable tool for selecting candidates for treatment with yttrium 90 ibritumomab tiuxetan (Zevalin) after relapse on standard chemotherapy, according to a study presented here at the Society of Nuclear Medicine 2008 Annual Meeting.

Paolo Castellucci, MD, from Policlinico S. Orsola-Malpighi, in Bologna, Italy, presented the findings from 38 patients with CD20-positive follicular NHL. His group has now evaluated the approach in 55 patients.

"In this disease, PET is really the only way to show the presence of relapse soon after treatment. These patients can then be treated with yttrium 90, so it is important for patient outcomes," Dr. Castellucci told Medscape Radiology.

FDG-PET was used to identify 38 patients with CD20-positive NHL as having relapsed on standard therapy. Patients were rescanned at 4 and 10 months after starting on ibritumomab.

In the documentation of relapse, PET identified the extent of disease as being limited to 1 side of the diaphragm in 20 cases (7 above and 13 below), involving nodal sites at both sides of the diaphragm in 11 cases, and involving the nodes and parenchyma in 7 cases. At the final assessment, radioimmunotherapy treatment resulted in complete remission in 21 patients (55%), partial remission in 13 (34%), and progressive disease in 4 (11%).

The investigators observed a higher rate of complete responses in patients with limited disease than in those with extranodal disease. In all cases, FDG-PET at 4 months was consistent with the clinical findings at follow-up. The extent of relapse correlated with the likelihood of complete response to radioimmunotherapy, Dr. Castellucci reported.

"We believe that FDG-PET is a valid tool for evaluating CD20-positive NHL, for both detecting relapse and documenting the response to radioimmunotherapy," he said. "We are beginning clinical applications now."

Peter Conti, MD, MD, PhD, professor of radiology, clinical pharmacy, and biomedical engineering at the University of Southern California School of Medicine, in Los Angeles, and past president of the Society of Nuclear Medicine, commented at a press conference that this study speaks to the emerging partnership between molecular-imaging technology and therapeutics.

"This study exemplifies the use of novel radioimmunotherapeutics with molecularly targeted agents combined with imaging technology to deliver personalized medicine based on extent of disease," he said.

He noted that as many as 90% of patients seen at PET-imaging centers are cancer patients. "This is a big field for nuclear imaging," he added, "and although the study is small, it contains a spectrum of cases and clearly shows relapse followed by a nice resolution of disease with treatment."

Dr. Conti disclosed relationships with Fluoropharma, Inc, Molecular Imaging Corp, NuView Radiopharmaceuticals, Molecular Insights, Inc, and Siemens.

Society of Nuclear Medicine (SNM) 2008 Annual Meeting: Abstract 584. Presented June 18, 2008.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.