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The FDA has just approved a new drug, Avastin, for the treatment of advanced colon cancer. Its ability to starve tumors and stop their growth means that cancer could become a manageable disease one day. We explored the benefits, potential uses, and risks of Avastin with Dr. Harold Burstein.
Moderator: Welcome back to WebMD Live, Dr. Burstein. The FDA has just approved the use of a new type of drug, Avastin, in the war on cancer. Avastin is an angiogenesis inhibitor. Can you explain what this means and why it is such an important breakthrough in cancer treatment?
Burstein: For several decades now there has been interest in targeting the blood supply that allows tumors to grow. Like all normal tissues tumors rely on blood supply for nutrients and oxygen to keep the cells alive. One of the early things that tumors do when they grow is promote new blood vessel formation to protect their supply. This process is called angiogenesis. For that reason people have been interested in blocking the growth of these new blood vessels feeding the tumor and have tried to develop drugs that would accomplish that. Avastin is the first such drug to show convincing clinical benefits.
Moderator: What kinds of clinical benefits were shown in trials?
Burstein: The study that led to FDA approval was a randomized clinical trial for patients with advanced colorectal cancer. These patients, who had not previously had chemotherapy for advanced cancer, were randomized to treatment with chemotherapy alone using a cocktail of three different chemotherapy drugs, or to that same cocktail in combination with Avastin. All these are intravenous treatments given in the outpatient clinic.
In the study patients who received chemotherapy and Avastin did better than patients who received chemotherapy alone. The patients receiving Avastin were likely to have longer tumor control and live longer than patients who did not receive Avastin. On average, they lived about five months longer. Because an improvement in survival is considered so important as an end point of cancer studies, the FDA approved this drug based on these findings.
Moderator: Avastin has been approved for use in treating metastatic colorectal cancer. Do you see it being tried for this type of cancer in an earlier stage?
Burstein: At present, the drug is only approved for use in advanced colon cancer. It remains to be seen how important the drug will prove to be in other tumor types.
There are intriguing data indicating that Avastin can slow down the growth of other cancers, including kidney cancer. There are many, many trials now looking at the role of Avastin with different chemotherapy cocktails or in different tumor types, such as lung, breast, and pancreas cancer. Many people hope that this strategy will be valuable in lots of different cancer types.
Moderator: Avastin has been described as a targeted drug -- does that mean fewer side effects?
Burstein: It means different side effects than standard chemotherapy. Avastin is actually an antibody that binds to a protein called VEGF (vascular endothelial growth factor). When Avastin binds to VEGF, it neutralizes the activity of VEGF. VEGF is one of the most important factors that promote angiogenesis.
The side effects of Avastin include:
Hypertension High blood pressure Nose bleeds and more rare problems, such as: Blood clots Bleeding Perforation of the bowel
Member question: Is VEGF present in any solid tumor?
Burstein: Many different solid tumors express VEGF. How important it is for each of these different tumors remains to be seen. Also, we don't know yet when the optimal time for use of a drug like Avastin will be. The study that led to FDA approval used Avastin for advanced colon cancer in patients that were chemotherapy naive. We don't know yet if it will be effective in patients whose tumors are refractory or resistant to chemotherapy, and similarly, there is not interest in trying this drug among patients who have earlier stage colorectal cancer.
Moderator: What is the dosing frequency of Avastin? Many cancer treatments are provided in the home setting by means of a home infusion company. Is Avastin a medication that will be dosed daily and self-injected by patients or caregivers in this home environment, similar to a neupogen therapy?
Burstein: No. Avastin is given in the doctor's office as an intravenous infusion once every two weeks. It is expected to become commercially available in wide supply within the next few months.
Member question: Why did they target colon cancer first to test the drug? Does colon cancer have special features?
Burstein: They are simultaneously testing this drug in lung, colon, breast, and other cancers. A year ago, results from a study treating advanced breast cancer in patients that had already received many chemotherapy treatments did not show a major effect of Avastin in that disease setting. Studies from lung cancer patients are still awaiting results.
Member question: Does Avastin cure colon cancer?
Burstein: While Avastin clearly helps people with colon cancer live longer, it does not as yet seem to cure colon cancer.
Member question: I read that the cost will be $44,000 per year. Does that mean you would have to get a shot every 2 weeks for the rest of your life?
Burstein: We don't know for how long to use Avastin optimally. At present, I would imagine that people would receive it every two weeks for quite awhile.
Member question: Would it help someone with stage IV colon cancer?
Burstein: The FDA approval was based on studies of stage IV colorectal cancer.
Member question: I read where the doctor who first proposed this approach (I've forgotten his name) said he expected it to be widely used for ovarian cancer. Are tests under way for ovarian cancer?
Burstein: I believe studies are underway for ovarian cancer.
Member question: Dr. Burstein, do you think that Avastin will be effective against prostate cancer, or will it be as useless as Atrasentan has eventually proved to be for advanced prostate cancer patients?
Burstein: It is too soon to say whether Avastin will be valuable in prostate cancer or most other types of cancer. We are all eagerly awaiting results from those studies that are ongoing.
Obviously, everyone will want to know what effect this drug might have on other common cancers. At present, the data are inadequate to suggest patients who have cancer other than colorectal cancer or perhaps kidney cancer should be receiving this drug.
Whenever there is a very exciting new product and, in particular, one that has a novel mechanism of action, like Avastin, there are always more questions than answers on how best to use this drug. It will take many years of research to fully understand and answer these questions. This drug is being studied in many, many clinical trials right now for all kinds of cancer. Patients who are interested in this drug should seek out those kinds of clinical trials as a very important way to think about their treatment.
Further, there are many other angiogenesis inhibitor-type drugs now in development. Patients should also consider trials involving those drugs, now that this approach seems to be valuable.
Moderator: How can a patient get involved in clinical trials?
Burstein: The first way is to talk to your oncologist. The second way is to seek out care at a federally designated comprehensive cancer center. The third way is to go to a valuable clinical clearinghouse, such as WebMD. The best place to go would be clinicaltrials.gov. That is the National Institutes of Health search engine and information page for clinical trials. If you punch in bevacizumab (that's the generic name for Avastin) you'll see no less than 36 trials.
Moderator: Thanks to Dr. Harold Burstein, for sharing his expertise with us today. For more information on everything he discussed today, be sure to visit him at his Cancer Treatments and Advances message board, where you can post questions for Dr. Burstein and get advice and support from fellow WebMD members.
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