The gadolinium safety debate took another turn Friday, when the FDA's Medical Imaging Drugs Advisory Committee (MIDAC) voted to recommend revisions to the prescribing information for MR contrast agents with the material.
The vote was to add a warning that gadolinium can be retained in some organs and tissues.
According to a response to the meeting by Guerbet, “There are two kinds of gadolinium based contrast agents [GBCAs], linear and macrocyclic. Although there are many similarities amongst these agents, they differ in their kinetic and thermodynamic stability. Linear GBCAs are generally less stable, and for this reason, more likely than macrocyclic agents to deposit gadolinium in tissue. Guerbet's GBCA, Dotarem [gadoterate meglumine] is a macrocyclic agent. The advisory would also state the risk of retention is slightly greater with linear agents versus macrocyclic ones.”
At the meeting, 13 committee members voted in favor of the proposal. "It was appropriate to state that there may be differences among these agents that need to be explored," said one, Dr. Michael Weisman, a professor of medicine at the University of California, Los Angeles, adding that, "It's also appropriate to state that risk strategies need to be looked at more carefully. There are populations that need to be addressed, such as those that may overutilize this type of contrast imaging."
The strongest – and only – dissenting vote came from Alicia Toledano, who is president of Biostatistics Consulting in Kensington, MD. She felt it did not go far enough.
"It is hard to dismiss an anecdotal report when you are the anecdote. A life ruined is a life ruined," she said. "What does a patient do when doctors and everyone she or he turns to for help 'pooh-poohs' his or her concerns and does not order a simple urine test? When a patient finally gets tested and is found to have gadolinium retention, there is no FDA-approved antidote. What does that patient do?"
She called the proposal “insufficient.”
The group was also unanimous at 15-0 in its vote requiring the agency to have contrast manufacturers do more studies to see if more regulation is necessary.
The group argued that more information is vital.
"It's clear we need more information," stated Dr. Peter Herscovitch, acting MIDAC chair and director of the PET department at the U.S. National Institutes of Health (NIH).
The votes followed a public hearing on retention that saw many emotional moments about adverse reactions, including from a representative of Gena Norris, the wife of famed action-star Chuck Norris. After a series of scans with gadolinium, she suffered severe abdominal pain.
She has resorted to treating her condition with an expensive professional hyperbaric chamber.
"My heart breaks for those who don't have the financial means they need," she added. "We will continue to use our platform to raise awareness about the dangers of gadolinium."
That said, despite the risks of retention, Dr. Elizabeth Morris, past president of the Society of Breast Imaging and a breast radiologist at Memorial Sloan Kettering Cancer Center, called its use essential and a “lifesaving test."
Also advising caution against an overreaction, Dr. Scott Reeder, of the University of Wisconsin, advised that, "it is important to consider the importance of the benefits of gadolinium in treating patients with a wide variety of diseases, as well as the standard safety record of these agents."