The genetically modified bone-growth compound used in Fridley-based Medtronic's InFuse spinal-fusion devices increases risks of cancer when used in high doses with high-risk patients, but careful doctors can mitigate those risks, a new analysis of hundreds of thousands of patients says.
Dr. Wellington Hsu, director of orthopedic surgery research at Northwestern University in Chicago, presented the results of his synthesis of several large-scale studies during a session at the annual meeting of the North American Spine Society in San Francisco on Friday.
Hundreds of millions of dollars and thousands of surgical outcomes are riding on the safety of bone morphogenetic protein (BMP), the chemically active ingredient in InFuse. Hsu's research, based on a survey of half a dozen studies covering many thousands of patients, supports Medtronic's main contention that InFuse doesn't increase cancer risks when spinal surgeons use it appropriately.
"My conclusion is that InFuse, when used judiciously and responsibly, does not increase your risk of cancer. But that there are [cancer] mechanisms that we need to be aware of," Hsu said. "I would still not recommend using BMP in somebody who has a history of cancer. But I believe that it is safe to use in proper doses in the general population."
While the results may be warmly received in Medtronic's sales department, some researchers remain skeptical of his survey's approach and his conclusion endorsing the broad safety of InFuse.
"If patients who the surgeons very likely selected for low risk of cancer ended up with about the same amount of cancer occurrence as people who have a normal cancer risk, I don't think that is an endorsement. I think that is a warning," said Dr. Eugene Carragee, an orthopedic surgeon at Stanford University and longtime InFuse critic. "Surgeons would not have applied the BMP with equal frequency in people with cancer risk because it was contraindicated."
InFuse is a device used to treat degenerative-disc disease by fusing together deteriorating vertebrae. It features titanium cages with sponges that deliver a manufactured human bone protein, BMP, which stimulates rapid bone growth at the spinal-fusion site.
According to the latest data, patients in the U.S. had about 80,000 spinal-fusion operations in 2011, and 27 percent involved BMP. Past studies have found many doctors used the device for procedures at higher doses than the Food and Drug Administration allows.
The device had been a major source of revenue growth for Medtronic until 2011, when the Spine Journal published critical articles that depressed InFuse sales.
The journal report suggested that Medtronic had covered up risks of BMP, including higher-than-expected incidence of cancer. The Spine Journal publication led to a 2,300-page report from the Senate Finance Committee documenting efforts by Medtronic's marketing department to influence early studies of InFuse to downplay cancer risks and generate strong sales.
Before the Spine Journal issue, InFuse had revenue approaching $1 billion a year, but income dropped off rapidly afterward. For the year that ended last April, Medtronic had just $471 million in InFuse sales, down 11 percent from the prior year. Medtronic earnings reports still blame flagging BMP sales for helping to stall financial performance of its entire spine division.
A cloud of litigation also is dogging InFuse. The company has set aside $140 million to potentially resolve about 4,800 patient claims stemming from a variety of alleged injuries from people with InFuse implants, securities filings say. Investors have filed lawsuits alleging executives harmed the value of the company with their handling of InFuse, and this summer the insurer Humana filed a racketeering lawsuit alleging Medtronic had promoted InFuse for uses not approved by the Food and Drug Administration.
Hsu confirmed past studies' findings that much higher concentrations of BMP create a stronger risk of cancer, particularly in Medtronic's proposed Amplify system, which was never put on the open market.
But he said the risk of cancer in InFuse patients seems to have dropped off, as the medical community slowly became aware that BMP should not be used in patients with a history of cancer.
"The complications that we used to see regarding BMP were probably a result of not understanding the potency of the product," he said. "Now that we have a better understanding, we are not seeing as many of these complications anymore."
Joe Carlson • 612-673-4779
Twitter: @_JoeCarlson
