The amino acid imaging agent O-(2-[18F]-fluroethyl)-L-tyrosine (F-18 FET) has diagnostic benefit for imaging pediatric gliomas when conventional magnetic resonance imaging (MRI) cannot make out a clear picture of the disease, according to new research. This study was presented at the 2013 annual meeting of the Society of Nuclear Medicine and Molecular Imaging, held June 8-12, 2013, in Vancouver, British Columbia.
Brain cancer imaging is often conducted with conventional MRI, but there are some limitations to this imaging technique. This type of cancer accounts for approximately 80% of all invasive brain tumors and develops in the brain’s glial cells that protect and maintain a state of neural equilibrium. Conventional MRI can sometimes over- or underestimate the extent of these tumors and the exact shape of their outlying margins.
Molecular imaging through positron emission tomography (PET), which provides information about physiological functions rather than structures of the brain, can be performed with a variety of imaging agents that bind to specific cellular systems. Brain imaging agents used include glucose, which indicates cellular metabolism, and amino acids, which indicate protein metabolism and are important in rapidly growing neoplastic tumors.
Amino acid PET imaging has been shown to be better than glucose imaging for detecting neoplastic tissue and treatment monitoring in cases of brain cancer. In general, the brain requires more glucose than other body tissues and organs, so brain scans are “noisier” and less defined than scans of other areas. In contrast, areas of increased amino acid activity show up clearly on scans as visual “hot spots.”
“In patients with brain tumors, contrast-enhanced structural MRI is currently the diagnostic method of choice. However, in youths with newly diagnosed cerebral lesions thought to be brain tumors, MRI’s ability to identify neoplastic tissue or tumor progression and recurrence after treatment is limited. F-18 FET is complementary and can potentially improve diagnosis and treatment of pediatric brain tumors,” said lead author Veronika Dunkl, MD, of the Institute of Neuroscience and Medicine, Forschungszentrum Jülich, in Jülich, Germany.
For this study, 15 young patients whose glioma cerebral cancer was suspected via MRI screening underwent PET imaging with the guidance of F-18 FET. This molecular imaging technique was 87% effective in detecting and differentiating brain lesions in children and young adults. The method was able to pinpoint 11 of 12 brain lesions correctly as tumors and 2 out of 3 as nontumorous growths.
Repeated PET imaging (17 scans) for seven more pediatric patients provided meaningful information about cancer progression or remission. F-18 FET imaging was able to detect residual tumor and tumor progression in 5 of 6 scans, and in 11 scans in which the cancer had been eradicated, for 94% accuracy.
“Results of the present study may improve the clinical management of this vulnerable patient population significantly, especially when a decision for further treatment is difficult or impossible on the basis of conventional MRI alone,” said Dunkl.