FDA Approves Gleevec for a Type of Abdominal Cancer ...
RightHealth and Healthology
The Food and Drug Administration has approved the targeted cancer drug, Gleevec...again. Last year Gleevec was approved in record time for a rare form of leukemia. Now, the pill, which attacks cancer cells and spares healthy cells, has been approved for a particularly lethal form of abdominal cancer. In clinical trials, the drug helped approximately 75 percent of patients suffering with advanced stage gastrointestinal stromal tumor, or GIST, a cancer that until now, has been nearly impossible to treat if not caught early.
Dr. George Demetri, the lead investigator in the Phase II international study, explains why this new development is so exciting to patients and researchers alike.
First, why is the oncology world so excited about the use of Gleevec for gastrointestinal stromal tumor?
Because now we have something that definitively, unquestionably works in the majority of GIST patients, where before all we had was the telephone to call our surgical friends. And many of our patients could not have any more surgery and we had nothing to offer them.
Could you describe this form of cancer?
GIST is a rare cancer of the abdominal contents. It can usually be of the stomach or the small intestines. Most of the common cancers in the intestines are the cells that line the intestines or the stomach. This is a cancer that actually occurs in the walls of the cells that hold it together.
What is special or unique about this type of tumor?
Any sort of standard chemotherapy has been totally useless against fighting GIST once it has spread beyond where a surgeon could take it out. Most of the patients in that case would have the disease rapidly progress and only have at most a couple of years of life to look forward to.
Is GIST hereditary?
It's extraordinarily rare for it to run in families. It's well understood now that the cause of this disease is a specific mutation that usually happens only in the tumor cells, not in other cells in the body that somebody could pass along to their children.
It turns out that the cancer cells have a problem in the DNA that then gets made into an overly active enzyme that's called KIT. That sits on the surface of the cancer cells. This enzyme then sends a signal in an uncontrolled way inside the cells and keeps the cells alive and keeps the cells growing which is fundamentally what cancer is -- a cell of uncontrolled growth.
What is most often the prognosis for a person diagnosed with GIST?
The prognosis depends on how big the tumor is at the time of diagnosis. We're actually finding GIST at an earlier stage now. A tumor that is about a half inch or a tenth of an inch can be cured by surgery alone.
What we're worried about are the larger GISTS, which may be 10 or even 20 inches big by the time they're found. Those tumors are at extremely high risk of spreading to other parts inside the abdomen, or to the liver. In those cases, before the year 2000, the disease was uniformly fatal.
We've all been hearing a lot about the promise of targeted therapies. How do they work?
Targeted cancer drugs home in on the cancer cells, and leave the normal cells alone. It makes sense that if a cancer cell is growing uncontrollably, it must have some switch that's been left on, that normal cells have a tendency to control. We are finding those switches that are mutated or uncontrolled in the cancer cells, and finding ways to control the switches. That's what targeted therapy is all about.
Could you describe some of the clinical trial results?
Approximately 55 percent of patients who received Gleevec have had their tumors shrink more than 50 percent -- some of them more than 80 percent, and that's been sustained over time. These are people who would have died within a series of months had they not had access to this drug. At least another 30 percent of patients have had their tumors completely stop growing and stabilize. They may not be shrinking, but the tumors are not getting worse and these people are back to having a very nice quality of life.
What are the side effects of Gleevec for these patients?
Well one reason we're all so excited about it is that the drug is very, very tolerable. People take it in capsules once or twice a day. They don't think much about it. It does have some side effects. But compared to chemotherapy side effects, it's much gentler.
The biggest side effect is fluid retention in different areas of the body. Most people get a little puffiness under their eyes or around their eyes.
Some people can also have some edema or swelling in other parts of the body, say, for example, in the ankles. Other people have noticed some minor diarrhea that comes on a couple of hours after the pills are taken. But that can be treated and prevented with some over-the-counter antidiarrheal medicines like Imodium that anyone can pick up at a local pharmacy.
Other people have had a little bit of acid indigestion feelings, which again are very mild. There has been a bit of fatigue with some people. There has been a little bit of rash. In rare cases, people can have a more severe rash, but it can be managed by changing the dose.
Some of the patients have had some gastrointestinal bleeding as well, which might just be coming from too much of a good thing. Some of the patients in our studies had tumors the size of small watermelons in their bellies. As these tumors rapidly shrink, they can burst blood vessels, which can lead to some intra-abdominal bleeding. So this side effect probably has more to do with very rapidly shrinking tumors than anything else.
For the patient, what are the practical differences between this oral therapy, and standard therapies like chemotherapy and radiation?
It is an incredible quality of life benefit to feel that you're in control of your own life -- not tied to the doctor's offices or to a nurse whose always poking into your vein to give you intravenous treatment. And there is the physical benefit of not having to endure all the antinausea medicines that go along with chemotherapy.
How long do patients have to be on treatment?
No one knows the answer. At this point, we envision that patients may well have to take this drug for a lifetime. As long as it keeps controlling the tumor, we see no particular problem with that.
Will it be used in combination with other therapies?
Absolutely. Physicians developing this drug for leukemia are testing it now in combination with chemotherapy. Our studies at Dana Farber are just about to open to test the safety of Gleevec with chemotherapy in a variety of patients.
The idea is clear. Although we know that we can shut off the one signal by shutting down this enzyme, it strikes us all as reasonable to think that if we can also kill the cells by a different mechanism (maybe by some very low dose or gentle chemotherapy along with the Gleevec), maybe we'll do better in terms of controlling the disease or preventing the disease from coming back in those patients.
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