FDA Approves PET Imaging Agent for Prostate Cancer

Roxanne Nelson


September 12, 2012

September 12, 2012 — The US Food and Drug Administration (FDA) today approved the production and use of a new positron emission tomography (PET) imaging agent, Choline C 11 Injection, which will be used to help detect recurrent prostate cancer.

Administered intravenously, Choline C 11 Injection produces an image that helps locate specific sites in the body for follow-up tissue sampling and testing in men with suspected recurrent disease.

The approval is limited to Choline C 11 Injection produced by the Mayo Clinic of Rochester, Minnesota.

"Choline C 11 Injection provides an important imaging method to help detect the location of prostate cancer in patients whose blood tests suggest recurrent cancer when other imaging tests are negative," said Charles Ganley, MD, director of the Office of Drug Evaluation IV at the FDA's Center for Drug Evaluation and Research, in a statement.

The FDA's approval of Choline C 11 Injection "provides assurance to patients and health care professionals they are using a product that is safe, effective, and produced according to current good manufacturing practices," he added.

Choline C 11Injection is a radiotracer consisting of choline labeled with the positron-emitting isotope carbon C 11. It integrates into tumor cells via an active, carrier-mediated transport mechanism for choline, according to the National Cancer Institute (NCI). The substance then undergoes intracellular phosphorylation by choline kinase, an enzyme that is often upregulated in human cancers. The end result is phosphoryl C-11 choline. Tumor cells show a higher rate of C-11 choline uptake and incorporation, as their proliferation is much higher than normal cells, thus allowing for PET imaging.

Studies Confirm Efficacy

The FDA has confirmed the safety and effectiveness of Choline C 11 Injection by a systematic review of the published literature. The analysis included 4 independent studies, with a total cohort of 98 patients with elevated blood prostate-specific antigen (PSA) levels but without any signs of recurrent disease or sign of recurrent prostate cancer on conventional imaging. PET imaging using Choline C 11 Injection was then performed, and those who had abnormalities detected on PET scanning underwent tissue biopsy.

In each one of these studies, at least half of the patients who had abnormalities detected on PET scanning with the new agent also were confirmed to have recurrent prostate cancer, following pathology testing of the abnormal tissue.

However, PET scan errors also were reported. While it varied across studies, false positive PET scans were observed in 15% to 47% of patients, thus underscoring the necessity for confirmatory tissue biopsy.

According to the FDA, Choline C 11 Injection must be produced in a specialized facility and administered to patients soon after it is produced. Even though PET imaging with Choline C 11 Injection has been used at several institutions during the past few years, none have been approved by the FDA to manufacture the agent. The Mayo Clinic PET Radiochemistry Facility is the first FDA-approved facility for the production of Choline C 11 Injection.

The Mayo Clinic has conducted studies with Choline C 11Injection, 3 of which were presented at this year's annual meeting of the American Urological Association.

"Taken together, the three studies represent an important validation of the C-11 choline PET/CT scan as an evaluation tool for patients with prostate cancer," said Jeffrey Karnes, MD, from the Mayo Clinic and senior author of all 3 papers, in a press release. "We believe the use of these scans can improve the evaluation and treatment of this common form of cancer, while potentially reducing the cost of delivering the best possible care."

Uncommon mild skin reactions at the injection site were the only adverse effect attributed to the use of Choline C 11 Injection.