THURSDAY, Aug. 26, 2004 (HealthDayNews) -- A recent warning that the colorectal cancer drug Avastin has life-threatening side effects seems unlikely to change its application, experts say.
"We will continue to use the drug," said Dr. Peter Kozuch, an attending physician at St. Luke's-Roosevelt Hospital and Continuum Cancer Centers of New York in New York City. "It represents an important option in the treatment of metastatic colorectal cancer."
The U.S. Food and Drug Administration approved the drug in February to treat colorectal cancer that had spread to other parts of the body. According to product information, Avastin is a monoclonal antibody that cuts off blood supply to cancer cells. In pre-approval studies, researchers found Avastin, in combination with chemotherapy, gave patients an extra five months of life.
But earlier this month, the FDA and Avastin's manufacturer, Genentech Inc., alerted health-care providers that the drug carried with it a heightened risk of blood clots, which can lead to stroke, heart attack and chest pain. The warning letter to doctors, to be followed by new drug labeling, said the risk of serious heart problems was doubled for cancer patients who took Avastin with their chemotherapy.
In the research on which the approval was based, a small number of such "events" was noted, Dr. David Ross, deputy director of the FDA's Office for Drug Evaluation 6, said.
Recently, newer study data showed that, in a trial of 200 people, 10 of those on Avastin (5 percent) had an adverse effect, compared to five in a control group.
Ross noted, however, that the newer group of people was older and more frail than those in the initial study.
But, he added, "The company's analysis of the data and the FDA's analysis, which is ongoing, is that there is enough data to update the labeling and focus on arterial [heart attacks and strokes] versus venous events. This is important information for providers to have."
"There were a small number of cases before, and now a small number of cases in a different patient population," added FDA spokesman Jason Brodsky. "Taken together, the prudent thing to do was to issue a warning and follow up with labeling revisions to reflect the new information."
Because labels take time to update and distribute, Genentech sent a letter to health-care providers on Aug. 12.
As the first monoclonal antibody approved for this type of cancer, Avastin is, in a way, a breakthrough drug. It is considered a "biologic" drug, meaning it's more targeted than previous generations of drugs. Still, Avastin is only approved for use in combination with traditional chemotherapy.
It is still not proven that the side effects seen are related to the drug or represent a statistical anomaly, Kozuch pointed out.
Regardless, any decision to use Avastin will clearly have to consider both risks and benefits.
"Avastin is indicated for a life-threatening disease, but these side effects are also life-threatening," Ross said. "The challenge is to individualize the decision for a particular patient."
Colon cancer is the third most common cancer among men and women in the United States, according to the American Cancer Society. ACS estimates say there will be 106,370 new cases in 2004.
Kozuch said, however, that even though colorectal cancer is extremely grave, there are patients who are asymptomatic. And the new warning may need to be addressed.
"They may have many months of good quality of life left and we would hate to diminish that for something catastrophic like a stroke," he said.
"We will have to have very careful discussions with patients regarding chest pain, heart attack and stroke," he added. "In patients who have recently had a heart attack or stroke, they may not want to take this drug."
More information
The National Cancer Institute has more on colorectal cancer.
