Avastin Gastrointestinal Perforation Risk Confirmed by Study

New research confirms that cancer patients treated with Avastin face a greatly increased risk of developing potentially deadly holes in the wall of their stomach, small intestine or large bowel, known as gastrointestinal perforation.

According to the study, published in the most recent issue of the medical journal The Lancet Oncology, researchers at Stony Brook University Cancer Center in New York found that side effects of Avastin, the brand name of the anti-angiogenesis drug Bevacizumab, can lead to a 167 percent higher risk of developing gastrointestinal perforations when the drug is taken together with chemotherapy.

While Avastin already has a black-box warning about the risk, the research is the first to first to establish the significant Avastin gastrointestinal perforation risk.

Avastin was approved by the FDA in 2004 for treatment of non-small cell lung cancer and colorectal cancer when combined with chemotherapy. The drug prevents the formation of new blood vessels in tumors, starving them and inhibiting their growth. It has been found to improve the survival rate of cancer patients when combined with chemotherapy.

Gastrointestinal perforations are holes in the walls of the stomach, small intestine or large bowel, which allow the contents to leak out into the abdominal cavity. This can cause bacterial contamination, a condition known as peritonitis. When the stomach develops perforations, gastric acid can leak into the abdominal cavity, causing chemical peritonitis. Such incidents are considered surgical emergencies that require immediate treatment.

The new study looked at 12,294 patients with a variety of solid tumors. Gastrointestinal perforation occurred in 0.9% of the patients being treated with Avastin, about twice the rate of those who did not take the drug. More than 20% of those cases were fatal.

The Avastin study also found a direct correlation with dosage and the types of tumors treated. When compared to those who did not take the drug, patients being treated with 2.5 mg/kg per week saw a 61% increase in the risk of gastrointestinal perforation from Avastin, compared with a 167% rate for those taking 5 mg/kg per week. Patients being treated for advanced colorectal cancer and renal cell cancer were found to also be at an especially increased risk, with patients treated for pancreatic cancer facing the lowest risk.

A prior study from Stony Brook in November 2008 indicated that Avastin can also increase the risk of blood clots by as much as one third, leading researchers to call for stronger warnings to be added to the drug’s label about the Avastin blood clot side effects.

In December 2008, the drug’s manufacturer, Genentech, sent a letter to doctors warning about Avastin problems linked to reports of serious eye inflammation when it is used off-labelm to treat wet macular degeneration. The manufacturer stated that it was aware of at least 38 cases of eye problems from Avastin use, with 32 of them involving severe inflammation.