Avastin can cause fatal side effects

Bevacizumab (brand name Avastin) has a controversial history. It was developed as a new kind of anti-cancer drug, and works by preventing new blood vessels from forming, starving a tumor of its blood supply. It was approved by the FDA in 2004 as a treatment for colon cancer, to be used alongside other chemotherapy drugs.

Despite positive early trials, bevacizumab struggled to live up to its promise. It slowed down the return of cancer, but several studies found that it didn't help patients live longer. The FDA went on to approve bevacizumab for patients with cancer of the kidneys, but originally rejected it as a treatment for breast cancer, before reconsidering, despite complaints from the Oncology Drug Advisory Committee (ODAC). The ODAC were concerned with the lack of survival benefit and the rare—but sometimes life-threatening —side effects.

A new study casts even more doubt on bevacizumab. Researchers have analyzed data on 10,217 people from 16 individual trials, and figured out that people being treated with bevacizumab are more likely to have fatal side effects.

People had a 2.5 percent chance of dying from a side effect while taking bevacizumab along with chemotherapy. The risk was just 1 percent for people having chemotherapy on its own. The people most at risk were those also taking chemotherapy drugs called taxanes or platinum drugs. Bevacizumab didn't seem to increase the risk of death for people taking other kinds of chemotherapy drugs. The most common fatal side effects of bevacizumab were severe bleeding, infections arising from having too few white blood cells, and a tear in the wall of the bowel.

It's difficult to say whether bevacizumab would have an overall benefit for some patients. For some groups of colon cancer patients, bevacizumab seems to prolong life by two or three months. But with uncertainty over whether it helps other groups of patients live longer, it's difficult to say whether it's worth running the risk of some dangerous side effects.

Bevacizumab is sometimes used to treat vision problems caused by the growth of new blood vessels in the eye (wet macular degeneration). The doses used in the eye are tiny compared with the doses used to treat cancer, so are unlikely to cause dangerous side effects.

What you need to know. Bevacizumab increases the risk of dying from side effects during treatment, particularly if taken alongside chemotherapy with taxanes or platinum drugs. If you're being treated for cancer and are considering bevacizumab, talk to the doctors treating you and make sure you get a realistic picture of both the benefits and the risks.

—Philip Wilson, patient editor, BMJ Group

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Read more on what you should know before starting treatment with Avastin.