The meetings, which continue Wednesday, came after The New York Times reported government scientists got nowhere when they raised concerns to the FDA about possible dangers of routine use of CT scans for colon cancer screenings.
The meetings represent a reassessment of risks associated with radiology at a time when average lifetime doses of diagnostic of radiation have soared.
About 70 million computed tomography scans are performed in the United States annually, up from 3 million in the early 1980s, and up to 14,000 people may die every year of radiation-induced cancers as a result, researchers say.
The Times cited FDA documents showing that after an agency official recommended approval of an application by General Electric to allow the use of CT scans for colon cancer screenings, Dr. Julian Nicholas, who was a gastroenterologist under contract with the FDA, said approving the application could "expose a number of Americans to a risk of radiation that is unwarranted and may lead to" abdominal cancer. The application is still under review.
FDA officials then told him to change his view, Nicholas said.
"I was first ignored, then pressured to change my scientific opinion, and when I refused to do that, I was intimidated and ultimately terminated," he said.
Experts differ on use of CT scans, particularly for healthy patients.
Alberto Gutierrez, deputy director of the FDA office that oversees radiological devices, said it's hard to say what's the best direction on CT scans for colon cancer.
Arvind Gopalratnam, a spokesman for GE Healthcare, wrote in an e-mail that research had shown that "CT colonography can be a very valuable, noninvasive screening tool to help diagnose colorectal cancer at early stages and ultimately improve overall survival rates."
A CT of a patient's abdomen is often used instead of a conventional colonoscopy, which is performed with a long, flexible tube with a camera inserted in a patient's colon.