Saturday, May 20, 2000
Colon cancer vaccine ready to test
Tristate team's drug to be used in clinical trials
By Tim Bonfield
The Cincinnati Enquirer
Foon
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A big step forward in cancer vaccine research, based on work done by a top Tristate cancer expert, will be announced today at a medical conference in New Orleans.
A nationwide, Phase III clinical trial is expected to begin this fall for a vaccine to prevent colon cancer from returning after surgery, said Dr. Kenneth Foon, the director of Cincinnati's Barrett Cancer Center and co-developer of the vaccine.
The trial will be sponsored by the National Cancer Institute and conducted by the American College of Surgeons Oncology Group, a network of several thousand cancer doctors. The five-year study will include about 1,400 colon cancer patients to be recruited from dozens of cities, most likely including some from Cincinnati.
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AT A GLANCE
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• What happened?
The National Cancer Institute has agreed to sponsor a large-scale study of a colon cancer vaccine that could prevent tumors from recurring after surgery. The trial, to be launched this fall, will be announced today in New Orleans.
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What does it mean?
While potentially helping many colon cancer patients, the study represents a major step forward in cancer vaccine research that could lead to vaccines for other types of cancer.
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What's next?
Patients cannot enroll in the study until this fall, when final wording of informed consent forms and other details are complete. The study will seek about 1,400 participants and take about five years to produce results.
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“We won't know if the vaccine really kills cancer cells until the end of the Phase III trial, but all the data we have to date is highly suggestive of a major clinical effect,” Dr. Foon said. “We have seen individuals who have done far better than would be expected under standard forms of care.”
Results from the large-scale test may be at least five years away. Still, the study is significant for several reasons:
• Despite years of interest in cancer vaccine research, this colon product is one of the few to reach the Phase III clinical trial level.
• If early results are confirmed, the vaccine could save thousands of lives among people stricken by the nation's fourth-leading type of cancer.
• Beyond helping people with colon cancer, a successful trial could accelerate vaccine work for other types of cancer, including compounds being studied at the University of Cincinnati.
Just reaching the Phase III clinical trial level makes many medical experts and health care consumers perk up their ears. That's because it takes years of testing — with positive results — just to reach this point.
“Phase III is where you start getting really large numbers of patients into studies,” said Cincinnati oncologist Dr. Rebecca Bechhold. “Many people can't get to the research centers that do Phase I and II studies but many Phase III trials we can bring right to our offices.”
While happy to see a potentially useful cancer weapon on the horizon, Dr. Bechhold warned that many Phase III trials end up proving that compounds don't work.
“The upside of this trial is that the toxicity risk appears minimal. So the study will probably fill up quickly,” Dr. Bechhold said. “But patients need to remember that the study is being done because we don't know what the results will be.”
In the U.S. system, drug research starts in the lab, then moves to animal testing, then into a three-level series of tests with human patients.
Tests to check for toxic side effects and safe dose levels are Phase I. Initial tests for effectiveness are called Phase II studies. Sometimes, Phase I and II studies are done together.
Only if a drug shows promise after all this testing can it go to Phase III, where hundreds, even thousands, of patients will try it.
The colon cancer vaccine was developed in 1989 by Dr. Foon and his research partner, Dr. Malaya Chatterjee, while working in Buffalo, N.Y. Later, the team worked together at the University of Kentucky, then moved to Cincinnati last year.
Dr. Foon became Barrett Center director in April 1999. Dr. Chatterjee joined the center soon afterward.
About 150 colon cancer patients have taken the vaccine, resulting in some hopeful signs.
For example, a woman whose colon cancer had spread to 22 lymph nodes and faced a better than 90 percent chance of recurrent cancer has lived seven years cancer-free since taking the vaccine after surgery, Dr. Foon said.
How the vaccine works
Unlike chemotherapy drugs that directly attack a cancer tumor, cancer vaccines attempt to prompt the body's own immune system to attack cancer cells. This has been very difficult to achieve, because cancer cells have proven adept at fooling the body into treating tumors as natural parts of the body.
Instead of using part of the cancer cell to trigger an immune response — the way many childhood vaccines work — the researchers created a mirror image of the target.
The vaccine's target is called carcinoembryonic antigen (CEA). This protein is found on every colon cancer cell.
But the immune system doesn't normally attack CEA. So the researchers injected mice with human CEA to generate an antibody to the target antigen — a mirror image.
Whether the immune response from mirror-image CEA is strong enough to kill cancer cells remains to be seen. Even if the vaccine proves successful, it won't be a full-blown cure.
Immune response alone will not be enough to destroy tumors once they have grown, Dr. Foon said. Instead the vaccine's goal is to kill off stray cancer cells in blood and other tissues that can't be removed by surgery.
Initial testing will focus only on those patients with stage III colon cancer — where surgery has removed all the tumors, but some lymph nodes have signs of cancer. Half will get chemotherapy. Half will get chemotherapy and the vaccine.
Dr. Foon hopes to cut recurrence rates that run as high as 40 percent to 30 percent or less.
If proven effective as a follow-up treatment, the vaccine might be considered for preventive use for high-risk colon cancer patients — much like the tamoxifen trials going on now for breast cancer.
Other vaccines
Drs. Foon and Chatterjee also have developed vaccines aimed at melanoma, breast cancer and lung cancer. A Phase III trial for the melanoma vaccine, to be run through the Southwest Oncology Group, one of the nation's largest cancer research networks, also has been approved by the National Cancer Institute and will start recruiting patients later this year.
The breast cancer vaccine remains in Phase II testing as a supplemental treatment to bone marrow transplant therapy.
Meanwhile, the Radiation Therapy Oncology Group, another national research network, is using the colon cancer and the breast cancer vaccines in combination as a possible lung cancer vaccine.
“I can't tell you how many companies are targeting vaccine therapies. But if this study proves the principle, there will be an explosion of research into cancer vaccines,” Dr. Foon said.
Colon cancer vaccine ready to test
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