Speeding Development Of Novel Tracer For Prostate Cancer

Researchers at Emory University in Atlanta, Ga., and at Nihon Medi-Physics’ research center in Chiba, Japan, collaborated closely in examining the potential of using the radiotracer FACBC to better stage or determine prostate cancer spread, said David M. Schuster, an assistant professor and director of the division of nuclear medicine and molecular imaging in Emory’s radiology department. “Our two studies show the progression of molecular imaging in what is called translational research, the process of taking research and finding useful applications for it with patients,” added co-author of “Initial Experience With the Radiotracer Anti 1-Amino-3-[18F]Fluorocyclobutane-1-Carboxylic Acid (Anti-[18F]FACBC) With PET/CT in Prostate Carcinoma.” Together with “A Preliminary Study of Anti 1-Amino-3-[18F] Fluorocyclobutyl-1-Carboxylic Acid for the Detection of Prostate Cancer,” the two papers illustrate the development of a promising radioisotope tracer (a radioactive substance) from in vitro stage (in a test tube) to in vivo (within a live subject) in animals to in vivo in individuals with prostate cancer, explained Schuster. The Emory pilot study with FACBC, performed with only 15 patients, shows that the amino acid analog may hold the potential to provide information to better stage or determine prostate cancer spread, said Schuster. He stressed that FACBC is not available for use with patients, and additional research needs to be done with larger groups of patients.

Other than skin cancer, prostate cancer is the most common type of cancer found in American men. Estimates show that there were more than 230,000 new cases of prostate cancer in this country last year, making it the third leading cause of cancer death in men. Schuster’s study is one of many in which researchers are exploring new and “better” radiotracers that could improve a physician’s ability to stage cancer, for example, by providing higher sensitivity. This is very important since treatment and recovery outlook are dependent on the stage of cancer, said Schuster. “FACBC could eventually provide additional anatomical information about cancer location,” he added, indicating that there could also be many “spin-off applications” for the tracer (for example, in patients with brain, breast and lung cancers). “This type of research is not a revolution, rather it’s an evolution; however, these kinds of evolutions can possibly lead to a revolution,” explained Schuster, who is also seeking additional funding for this research.

The two studies used FACBC with positron emission tomography (PET) and PET with computed tomography (PET/CT), both standard imaging tools that can be used to pinpoint diseases in the body. When PET is used to image cancer, a radiotracer is injected into a patient, and it is drawn in higher concentrations to cancerous areas. The highly sensitive PET scan picks up the metabolic signal of actively growing cancer cells. The CT scan generates a detailed picture of internal anatomy, locating and revealing the size and shape of abnormal cancer growths. When these two results are fused together, the functional data from the PET imaging are correlated with anatomy on the CT images to provide a single detailed and informative image.

Tracers—such as 18F-FDG, 11C-choline, 11C-acetate and others—are currently used for diagnosing prostate cancer, said Shuntaro Oka, veterinarian and an assistant research associate at Nihon Medi-Physics. In Oka’s in vitro and in vivo study, FACBC had a high accumulation in cancer cells, small excretion into the bladder and a low accumulation in areas of inflammation, indicating that it could possibly “overcome drawbacks of some traditional PET tracers,” he noted. “It is not unusual that the results of experiments lose touch with the results of clinical study; however, this time, the results of our basic studies correlated well with Dr. Schuster’s findings in patients with prostate cancer,” said Oka. “This is good news for development of our compounds,” he added, indicating clinical PET is not generally accepted in Japan; he hoped that FACBC could become “an agent to enhance the health and quality of life of patients.”

Oka said the two research studies were definite examples of molecular imaging, a technique to visualize the activity of molecules in the body. PET showed the activity of amino acid transporters that “mediate” FACBC, the radiotracer that was developed in Mark M. Goodman’s lab at Emory University, into prostate cancer. “ ‘Hot spots’ on FACBC PET indicate the location of the amino acid transporters in target tissue and the site’s increased activity of the amino acid transporters,” said Oka. Schuster indicated that the research was conducted with individuals representing “a panoply of clinical knowledge” from Emory Healthcare and Winship Cancer Institute of Emory University, Emory University, the Atlanta VA Hospital and Nihon.

The American and Japanese collaborative research appears in the January issue of the Journal of Nuclear Medicine, which is published by SNM, the largest molecular imaging and nuclear medicine association. Authors of “Initial Experience With the Radiotracer Anti 1-Amino-3-[18F]Fluorocyclobutane-1-Carboxylic Acid (Anti-[18F]FACBC) With PET/CT in Prostate Carcinoma” are David M Schuster, John R Votaw, Weiping Yu, Jonathon A Nye and Mark M. Goodman, Radiology Department, Division of Nuclear Medicine; Peter T Nieh, Viraj Master and Muta M. Issa, Urology Department; and F. DuBois Bowman, Biostatistics Department, all at Emory University in Atlanta, Ga.

“A Preliminary Study of Anti 1-Amino-3-[18F]Fluorocyclobutyl-1-Carboxylic Acid for the Detection of Prostate Cancer” was written by Shuntaro Oka, Ryota Hattori, Fumie Kurosaki, Masahito Toyama, Yasunori Yoshida and Osamu Ito, all with the Research Center, Nihon Medi-Physics Co. Ltd., in Sodegaura, Chiba, Japan; and Larry A. Williams, Weiping Yu, John R. Votaw and Mark M. Goodman, all with the PET Center and the Radiology Department at Emory University, in Atlanta, Ga.