Cancer drug Avastin linked to flesh-eating disease

The cancer-treatment drug Avastin has been linked to the rare but life-threatening infection necrotizing fasciitis, also known as flesh-eating disease, according to Health Canada, which issued a public warning Thursday.

In Canada, two patients on Avastin developed the disease, one of whom died. The cases came to light when the manufacturer, Hoffmann-La Roche Ltd, did a safety review.

The company identified 52 serious cases of necrotizing fasciitis worldwide between November 1997 and September 2012. Of the total, there were 17 fatalities, including the one death in Canada.

The risk of someone on Avastin developing the disease “is rare,” said company spokeswoman Nancy Zorzi, noting it occurs in less than 0.1 per cent of the cases.

As of late February, more than 1.3 million patients worldwide were being treated with the drug. In Canada, 5,000 to 10,000 patients annually receive Avastin, said Dr. Malcolm Moore, who heads the division of medical oncology and hematology at Princess Margaret Cancer Centre.

“This is an extremely rare complication of a very useful cancer treatment,” said Moore. “When you’re treating cancer you’re treating a life-threatening serious disease and all treatments of cancer are associated with a range of risks and side effects.

“You have to balance the risks and benefits. . . . And the benefits of Avastin, even given this serious toxicity, outweigh the risks.”

The warning, he said, would not alter the decision to use the drug for most patients with cancer.

In conjunction with Health Canada, the company issued a warning to health care providers Monday and released a public warning Thursday. In March, the U.S. Food and Drug Administration issued a similar warning.

Avastin is used to treat the brain cancer glioblastoma and used in combination with chemotherapy to treat metastasized colon, rectal and lung cancers. In Canada, it is commonly used to treat advanced colorectal cancer.

Patients on Avastin are at risk of gastrointestinal perforation, which is the development of a small hole in the stomach or intestines; fistula formation, an abnormal passage from one part of the body to another; and complications from wounds not healing properly. When the company examined its Avastin databases, it found that necrotizing fasciitis occurred in 21 patients as a consequence of those conditions. About two thirds of the cases involved patients being treated for colorectal cancer.

Necrotizing fasciitis is a severe bacterial infection of the skin and soft tissue. It can be brought on by a number of conditions and is commonly referred to as flesh-eating disease because it kills muscle and skin as it spreads.

The infection usually develops when bacteria enter the body from a minor skin injury or surgical wound. Symptoms can develop within 24 hours and include sudden, severe pain in the affected area, fever, redness, swelling or fluidfilled blisters in the skin, scaling, peeling, or discoloured skin.

Those with cancer are at greater risk of developing necrotizing fasciitis because their immune system is weakened due to chemotherapy.

In Canada, there are between 90 and 200 annual cases of necrotizing fasciitis, about 20 to 30 per cent of which are fatal.

The drug maker plans to update its product information to include a warning about necrotizing fasciitis.

Anyone on Avastin who develops symptoms of the infection — or any other unusual signs — should contact their health-care professional.