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PET scans may allow early prediction of response to targeted therapy of thyroid cancer

Reston, Va. (February 1, 2011) — Positron emission tomography (PET) can image metabolic changes following treatment with the protein kinase inhibitor vandetanib, helping to define the therapy response or the effectiveness of the therapeutic agent, according to research published in the February issue of The Journal of Nuclear Medicine. Currently being tested in clinical trials, vandetanib inhibits the function of the RET (rearranged-during-transfection protein) proto-oncogene and other protein kinases involved in the development and progression of cancer.

“For the most part, clinical trials have been measuring the effectiveness of vandetanib by changes in tumor size. Based on the activating effects of mutated RET and other protein kinases on numerous intracellular metabolic pathways, we hypothesized that PET imaging could play a role in the early evaluation of response to vandetanib,” said Martin A. Walter, MD, lead author of the study “Metabolic Imaging Allows Early Prediction of Response to Vandetanib.”

The study examined the usefulness of metabolic imaging to determine response to vandetanib in three ways. First, medullary thyroid cancer cells were used to create an in vitro model. After cultivation, the cells were treated with vandetanib, and changes in the metabolic profile of the cells were successfully monitored by transcriptional profiling and by radiotracer uptake studies.

Using the same untreated cells, the researchers then created an in vivo model by injecting mice with the cancerous cells and treating them with vandetanib. Small animal PET/computed tomography (CT) imaging was performed and was found to reproduce the in vitro findings of metabolic activity after three days.

Finally, a 43-year old patient with biopsy-proven metastasized medullary thyroid cancer was treated with vandetanib. PET scans taken at 12 and 24 weeks after treatment were able to detect metabolic response to vandetanib, consistent with the in vitro and in vivo samples.

“With the increasing number of available treatment options, careful patient selection is necessary to ensure targeted therapy is administered to those most likely to gain clinical benefit,” said Walter. “The identification of markers of treatment efficacy is a key factor for the success of these novel treatment approaches.”

“Furthermore,” he continued, “relating in-vivo PET imaging metabolic data with transcriptional profiling data using cluster analysis is an innovative concept that allows much potential in the field of molecular imaging.”

Authors of the scientific article, “Metabolic Imaging Allows Early Prediction of Response to Vandetanib” include: Martin A. Walter, Institute of Nuclear Medicine, University Hospital, Bern, Switzerland, and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, Calif.; Matthias R. Benz, Isabel J. Hildebrandt, Rachel E. Lang, Michael E. Phelps and Johannes, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, Calif.; Verena Hartung and Andreas Bockisch, Institute of Nuclear Medicine, University Hospital, Essen, Germany; Robert D. Damoiseaux, Molecular Shared Screening Resources, UCLA, Los Angeles, Calif.; and Wolfgang A. Weber, Department of Nuclear Medicine, University Hospital, Freiburg, Germany, and Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, Calif.

Please visit the SNM Newsroom to view the PDF of the study. To schedule an interview with the researchers, please contact Susan Martonik at (703) 652-6773 or [email protected]. Current and past issues of The Journal of Nuclear Medicine can be found online at http://jnm.snmjournals.org.

About SNM — Advancing Molecular Imaging and Therapy

SNM is an international scientific and medical organization dedicated to raising public awareness about what molecular imaging is and how it can help provide patients with the best health care possible. SNM members specialize in molecular imaging, a vital element of today’s medical practice that adds an additional dimension to diagnosis, changing the way common and devastating diseases are understood and treated.

SNM’s more than 17,000 members set the standard for molecular imaging and nuclear medicine practice by creating guidelines, sharing information through journals and meetings and leading advocacy on key issues that affect molecular imaging and therapy research and practice. For more information, visit http://www.snm.org.



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