The U.S. Food & Drug Administration (FDA), yesterday, approved an imaging agent known as Choline C11 Injection for “production and use” to detect recurrent prostate cancer in men receiving positron emission tomongraphy or PET scanning.
Although the use of [11C]choline has been carried out for some years at certain specialized centers in the USA and around the world, we believe that this is the first time that the agent has been formally approved by regulatory authorities for use as an imaging agent, and the current approval is limited to a single manufacturing site — at the Mayo Clinic in Rochester, Minnesota. According to the media release issued by the FDA,
Choline C 11 Injection must be produced in a specialized facility and administered to patients shortly after its production. While PET imaging with Choline C 11 Injection has been performed at a few facilities over the past several years, none of these facilities were approved by the FDA to manufacture the agent. The Food and Drug Administration Modernization Act directed the agency to establish appropriate approval procedures and current good manufacturing practice requirements for all PET products marketed and used in the United States. The Mayo Clinic’s PET Radiochemistry Facility is now the first FDA-approved facility to produce Choline C 11 Injection.
The approval is limited to the use of [11C]choline in men with a rising PSA after prior treatment for prostate cancer who are undergoing PET scans in an attempt to detect tumors that are not detectable by conventional scanning methods (e.g., bone scans and CT scans). The FDA is also very clear that [11C]choline-facilitated PET scanning is associated with a significant risk for false positive results, at that all patienst having a positive scan result should also have “confirmatory tissue sampling of abnormalities detected”.
This approval is based on data from four small, independent studies in just 98 patients with elevated blood PSA levels but no sign of recurrent prostate cancer on conventional imaging. All 98 patients underwent tissue sampling of the abnormalities detected on their PET scans. The studies showed that
- At least half the patients who had abnormalities detected on PET scans also had recurrent prostate cancer confirmed by tissue sampling of the abnormal areas.
- False positive PET scans results were observed in between 15 and 47 percent of the patients (depending on the study).
- The only adverse effect reported in these studies was a mild and uncommon skin reaction at the injection site.
What is not yet clear is the effect that this approval may have on the use of [11C]choline-facilitated PET scanning at other centers in the USA. [11C]Choline must be used within a relatively brief time period after its manufacture, and so it is not evident that the Mayo Clinic will be able to provide product for use at other PET scanning centers. On the other hand, those other centers may now only need to receive approval of their manufacturing facilities since the FDA has approved the actual product for clinical use. As of 7:30 a.m. this morning, there has been no statement from the Mayo Clinic about whether they will be able to manufacture and ship [11C]choline for use at other PET scanning centers.