Kate Johnson

June 10, 2015

BALTIMORE — By shuttling the imaging bed backward and forward during positron emission tomography (PET) scanning, it is possible to obtain whole-body dynamic images of both primary tumors and metastases in lung cancer patients.

"This option is now available in commercialized clinical scanners," reported lead investigator Ning Guo, PhD, from Massachusetts General Hospital and Harvard Medical School, in Boston.

She was presenting the findings here at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting.

These whole-body PET images use the 68Ga-PRGD2 tracer, a radiolabeled RGD peptide that binds to integrin, which indicates tumor angiogenesis. This allows clinicians to compare the behavior of primary vs metastatic tumors, which can often be heterogeneous, noted the session moderator, Victor H. Gerbaudo, PhD, associate director of the Center for Pulmonary Functional Imaging in Oncology, Brigham and Women's Hospital, in Boston.

"That type of discrepancy is extremely important when we're treating patients, because if we're going to be using antiangiogenic, integrin-based treatment and the primary is in fact uptaking the tracer but the met is not, then the problem that we have is that we're going to have something we call recurrence when in fact we never treated it in the first place," he commented after the presentation.

"The clinical potential of this technique is that it could help predict response to therapy," Dr Gerbaudo told Medscape Medical News. "It could aid personalized medicine by selecting patients that will benefit from antiangiogenic therapy based on integrin antagonism. On the other hand, it could identify in one imaging session those patients who will not benefit, if incongruence of binding potential is identified between the primary tumor and the metastases. In this group of patients, complete response to antiangiogenic therapy will not be achieved."

First Whole-Body Study With Reversible Tracer

"For patients with multiple tumors, this technology could significantly improve the contrast and quantitation of their PET scans and, therefore, the quality of their care," said Dr Guo in a press statement at the meeting. "RGD imaging could contribute to earlier diagnosis and more accurate prognosis by not only discriminating between benign tumors, inflammation, and malignancy but also providing insight about malignant lesions that are atypical or unclear ― a common challenge when using FDG-PET."

The study included 16 lung cancer patients who received 60-minute whole-body scans in four different positions using the 68Ga-PRGD2 tracer. The dynamic images both identified and quantified integrin expression in primary and metastatic tumors. The results were verified against traditional FDG-PET scans performed in each patient within 3 days.

"To the best of our knowledge, this is the first whole-body parametric imaging study of reversible tracer in...primary and metastasis lesions all over the body," noted Dr Guo.

"The same technology could be used [with] other tracers or other clinical applications in nuclear medicine and molecular imaging," she added.

Dr Guo and Dr Gerbaudo have disclosed no relevant financial relationships.

Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2015 Annual Meeting. Abstract 122. Presented June 8, 2015.

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