Study Probes Avastin's Risk to Gut

May 24, 2009 -- A new report confirms a link between the cancer drug Avastin and a risk of developing potentially life-threatening holes (perforations) in the gastrointestinal tract.

That risk is already noted in a "black box" warning -- the FDA's sternest warning -- on Avastin's label.

Avastin is approved to treat several types of cancer: metastatic colorectal cancer ("metastatic" means the cancer has spread), non-squamous non-small-cell lung cancer, metastatic breast cancer in certain patients, and glioblastoma (a type of brain cancer).

Avastin is an anti-angiogenesis drug. It blocks a protein called VEGF in order to thwart the growth of new blood vessels that supply blood to tumors.

The new report, published online in The Lancet, uses data from nearly 12,300 cancer patients in 17 trials, including 6,490 patients who took various doses of Avastin.

The researchers, who included Sanjaykumar Hapani, MD, of Stony Brook University Medical Center, pooled data from all 17 studies and confirmed that patients taking Avastin were more likely to develop gastrointestinal perforations. 

Most patients taking Avastin didn't develop gastrointestinal perforations, but about 1% of them did, which is about twice the rate that occurred among patients not taking Avastin.

Among all patients who developed gastrointestinal perforations, nearly 22% of those taking Avastin died, compared to about 16% of patients not taking Avastin.

Gastrointestinal perforations were more likely to develop in patients taking higher doses of Avastin, in patients with cancer that had spread (metastatic cancer), and in patients with certain types of cancer -- specifically, colorectal cancer and kidney (renal) cancer.

Hapani and colleagues note that they don't know exactly how Avastin increased the risk of gastrointestinal perforations.

Avastin is supposed to be stopped in patients who develop gastrointestinal perforations. But Hapani's team writes that that may be an "oversimplified" approach that "might reduce the use of an otherwise effective drug in patients with metastatic cancer and very few treatment options."

Hapani and colleagues call for further studies to see if low doses of Avastin might be OK after gastrointestinal perforations heal in patients with metastatic cancer.

In The Lancet, one of Hapani's colleagues notes financial ties to several drug companies, but not to Genentech, Avastin's maker.

In response to Hapani's report, Genentech spokeswoman Kristina Becker, MPH, tells WebMD in an email that the results "are consistent with what is already described in the prescribing information" for Avastin. She also points out that few patients developed gastrointestinal perforations at either dose, and that "the findings do not affect the safety or efficacy of Avastin in its FDA-approved indications."