Doctors treating cancer patients with Avastin are being warned that the medication has been linked to rare cases of necrotizing fasciitis, the infection better known as flesh-eating disease.

Avastin’s manufacturer, Hoffmann-La Roche Ltd., says it has identified 52 patients worldwide who developed necrotizing fasciitis while taking Avastin between November 1997 and September 2012.

Two of these infections occurred in Canada, including in one patient who died.

The medication, whose drug name is bevacizumab, is also used in much smaller doses as a treatment for an eye disease called age-related macular degeneration. But all of the infections occurred in patients being treated with Avastin for cancer.

The U.S. Food and Drug Administration published a similar warning in mid-March about the risks of flesh-eating disease in cancer patients taking Avastin.

It noted that the infections had been seen mainly in people with certain internal bleeding conditions or who had problems with wound-healing.

In Canada, Avastin is primarily used to treat colorectal cancer that has spread elsewhere in the body. It can also be used to treat metastatic lung cancer, ovarian cancer and certain forms of brain cancer.

Dr. Malcolm Moore, a medical oncologist at the Princess Margaret Cancer Centre in Toronto, says Avastin helps extend the survival of patients with metastatic colon cancer because it helps prevent the formation of new blood vessels in tumours.

But it also slows wound healing, which is why patients with recent injuries or surgeries, he says.

Flesh-eating disease occurs when bacteria enter the blood, often through a cut or even through an a wound as small as an insect bite mark. The most common bacterial culprit is Group A Streptococcus, a family of bacteria that can everything from strep throat to pneumonia.

Moore notes that patients taking Avastin are usually also taking other chemotheraphy drugs that suppress the immune system, making it easier for the flesh-eating bacteria to take hold.

Despite this small risk for infection, Moore says Avastin is still a very useful drug for colorectal cancer and its benefits outweigh the risks.

Necrotizing fasciitis is the disease that forced the amputation of one former Quebec premier Lucien Bouchard’s legs in 1994. It is also led to the 1990 death of Muppets creator Jim Henson.

People with diabetes are at a higher risk of developing necrotizing fasciitis due to their compromised immune systems.

Health Canada says doctors treating patients taking Avastin should watch for signs of bacterial infection in patients. As well, if patients develop flesh-eating disease, their Avastin should be immediately discontinued.

Hoffmann-La Roche said Avastin’s package insert -- called the product monograph -- will be adjusted to reflect the new warnings.