Avastin Shows Mixed Results Against Different Cancers
WEDNESDAY, Feb. 19, 2014 -- Clinical trials investigating new uses for the anti-cancer drug Avastin have produced mixed results.
When combined with standard chemotherapy, Avastin extended the survival of patients with advanced cervical cancer by nearly four months, doctors reported in one trial.
However, two other trials found the drug proved of little use in treating newly diagnosed glioblastoma brain tumors.
All three studies appear in the Feb. 20 issue of the New England Journal of Medicine.
Avastin (bevacizumab) slows or halts cancer progression by preventing the creation of new blood vessels that provide the tumor with nutrients and oxygen.
The U.S. Food and Drug Administration has approved Avastin's use in combination with standard chemotherapy in treating some forms of colon, lung, kidney, ovarian and breast cancer. It also has been approved to treat recurring glioblastoma.
Cancer doctors hailed the drug's success in extending the lives of women with recurring or persistent cervical cancer.
"We've been trying to find a way to improve survival in cervical cancer for a very long time," said Dr. Don Dizon, an oncologist at Massachusetts General Hospital and a gynecologic cancer expert for the American Society of Clinical Oncology. "We haven't been able to make much progress. We've tried many different drugs and nothing has been successful." He was not involved with the current study.
Avastin extended survival by 3.7 months for these patients, the researchers reported. The U.S. National Cancer Institute funded the trial.
While four months does not seem like a long time, study co-author Dr. Lois Ramondetta said this amount of added lifespan could provide a crucial window for trying other treatments that could cure or slow the cancer.
"We have a new backbone for adding additional drugs to, to produce even longer survival," said Ramondetta, a professor at the University of Texas M.D. Anderson Cancer Center and chief of gynecologic oncology at Lyndon B. Johnson General Hospital, in Houston.
But there are drawbacks. Avastin is very expensive, with two 16-milliliter vials of the drug currently priced at more than $5,400.
Given that cervical cancer is preventable through pap smears and HPV vaccination, Dizon questioned whether such an expensive drug would be affordable for women who couldn't afford the basic preventive medicine that could have kept the cancer from occurring in the first place.
"If you can't afford screening with pap smears, it's unlikely you'll be able to provide women bevacizumab as treatment," he said.
Avastin also increased the risk of troubling side effects, including high blood pressure, thromboembolisms [clots in blood vessels] and holes in the gut called fistulas.
Lead author Dr. Krishnansu Tewari noted that these side effects did not include death, and contended that the increase in side effect risk was moderate and acceptable.
"We feel with this study, we've shown this drug can improve survival," said Tewari, a gynecologic oncologist at the University of California, Irvine, Medical Center. "If we're preserving their lives so future therapies may be able to confer some benefits, we have the potential to turn this disease into a chronic disease."
The two drug trials involving glioblastoma followed up on earlier research that showed Avastin might be useful in treating recurring brain tumors.
Given that success, researchers wanted to see if the drug could serve as a first-line therapy that could be used with standard radiation and chemotherapy to treat newly diagnosed glioblastoma, said Dr. Mark Gilbert, lead author of one of the trials.
The trials found no survival benefit in using Avastin on newly diagnosed glioblastoma patients, however. The U.S. National Cancer Institute sponsored one trial, while the other was sponsored by the drug's manufacturer, Roche.
"We were surprised that we did not see a significant patient benefit," said Gilbert, a neuro-oncologist at the M.D. Anderson Cancer Center.
Gilbert speculated that Avastin might not be as useful in treating new tumors because standard therapy calls for surgical removal of the cancer prior to chemotherapy. In his trial, more than 60 percent of patients had their tumors completely removed, and another 30 percent had most of the cancer removed, he noted.
With the tumors gone, Avastin may not have been as effective in preventing blood vessel growth to cancer cells, he said.
The drug still could prove useful in treating new glioblastoma patients whose tumors cannot be surgically removed due to their location in the brain, he suggested.
"In that scenario, is there a role? The answer is, don't know, but it's certainly worth asking," Gilbert said.
He added that patients taking Avastin alongside chemotherapy also showed increased symptoms, worse quality of life and a decline in their ability to think and reason. Doctors can't tell whether these are side effects of the drug or an indication that the cancer continued to progress but the growth was cloaked by Avastin's ability to restrict blood vessel development, Gilbert said.
For more about Avastin, visit the U.S. National Cancer Institute.
Posted: February 2014