Cancer Study to Focus on PET Scans
By JENNIFER CORBETT DOOREN
February 21, 2006; Page D4
WASHINGTON -- The government will soon begin an effort to study whether a newer imaging technique that involves a PET scan can lead to better, more individualized cancer treatments.
Experts plan to meet next month to discuss adding a PET-scan project to existing clinical trials for non-Hodgkin lymphomas. The group -- including representatives from the Food and Drug Administration, the National Cancer Institute, Medicare, patient-advocacy groups, drug makers -- along with private researchers, wants to see if a PET scan can show whether the treatments being studied are killing the tumors. Eventually, researchers hope to look at other tumor types such as lung and breast cancer.
Currently, the PET, or positron emission tomography, scan is used to detect cancerous tumors, but it isn't widely used to track how well a cancer treatment is working. The FDA also doesn't accept PET-scan data from drug makers that file applications for approval of cancer drugs. The FDA accepts only older imaging methods such as a CT or CAT scan to demonstrate whether a tumor has responded to a drug.
The long-term goal of the scanning study would be for a cancer patient to be scanned after a few rounds of chemotherapy or other cancer treatment to see if the tumor is shrinking, rather than being scanned several weeks or months after treatment. A drug's dose could be adjusted or changed, based entirely on the scan's results.
The short-term goal of the non-Hodgkin lymphomas PET-scan project would be to qualify PET scans as an acceptable method to show whether a drug is shrinking a tumor when the FDA is evaluating drug applications. Non-Hodgkin lymphomas is a cancer of the lymphatic system and typically involves tumors in the lymph nodes that are located in various parts of the body. About 56,000 new cases are diagnosed annually in the U.S.
A PET scan, which is often combined with a CT scan, lets doctors see inside a tumor. Patients undergoing the exam are injected with a radioactive dye that contains glucose, or sugar. Cancer tumors absorb the sugar, which then shows up on the scan. Patients are placed on a table that's run through the scanner, which is about the size of a large tire. Older screening methods like X-rays and CT, or computed tomography, scans show more of an outline of the tumor and its location in the body.
Janet Woodcock, the FDA's deputy commissioner for operations, said a tumor could be dead on the inside after a patient receives treatment, but still show up on a CT or X-ray and look like it wasn't responding to treatment.
"What we want to do is distinguish better between living and dead tissue," she said, explaining that a living tumor will absorb the glucose during a PET scan while parts of the tumor that are dead won't. Several studies have suggested that PET scans are equally or more effective at showing tumor changes than CT scans, but the researchers involved in those studies suggested that larger studies be conducted. Now, such studies are set to get under way.
While drug companies like Pfizer Inc. have started using PET scans during the drug-development process as it did with its new cancer drug Sutent, the data weren't accepted by the FDA. Pfizer had to submit the CT-scan data.
The FDA typically approves a cancer treatment if drug companies can show the drug can either shrink a tumor or slow its growth.
Dr. Woodcock said if the PET-scan project shows that the scans are better or equal to CT scans at showing tumor shrinkage in patients with non-Hodgkin lymphomas, the agency will be able to adopt new guidelines and accept PET-scan data from drug makers.
Lou DeGennaro, senior vice president for research at the Leukemia & Lymphoma Society, said the PET-scan project would likely have an immediate impact on the amount of time that is cut off the drug-development process. For example, he said patients in clinical trials are typically given a round of treatment and then given a CT scan 26 weeks later. He said a PET scan would likely be given at six weeks to see if the tumor is responding. His organization is funding the cost of next month's meeting. The cost of adding the PET scan to certain clinical trials is likely to be paid for by the government and the pharmaceutical industry.
Officials from the Centers for Medicare and Medicaid Services are involved in the project because if the PET-scan data continue to suggest PET scans are effective at showing how tumors respond to treatments, the agency would be able to more quickly decide whether to pay for additional scans for Medicare recipients.
George Demetri, a cancer researcher at Dana Farber Cancer Institute and Harvard University, said he used PET scans during clinical studies of Sutent and Novartis AG's Gleevec for patients with a rare type of stomach cancer and could see changes in tumor response to the medication after just 24 hours in some cases.
While PET scans are promising, Dr. Demetri said the FDA should be conducting the additional studies of the scans in non-Hodgkin lymphomas and cancers before accepting the method.
Richard Frank, vice president of medical and clinical strategy for GE Healthcare, the top PET-scan maker, said companies are increasingly using PET scans in the drug-development process and can tell much sooner if a potential drug is going to work. GE Healthcare is also developing imaging agents that would be able to show more parts of tumors, such as blood-vessel involvement.
Write to Jennifer Corbett Dooren at
jennifer.corbett-dooren@dowjones.com
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