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New shot at cancer

Experimental vaccines aimed only at malignant cells show promise.

March 17, 2003|Linda Marsa | Times Staff Writer

It seemed like such a sensible way to fight cancer: Enlist a patient's immune system to attack malignant tumors. But sensible doesn't necessarily mean easy -- and scientists' attempts to elicit such a tumor-fighting response have been fraught with disappointment for decades.

Today, however, as scientists gain a deeper understanding of how the human immune system works, a new generation of experimental cancer vaccines are showing promise as potentially safer and more effective treatments for many types of malignancies.

Researchers at major medical centers across the country -- including several institutions in Southern California -- are reporting encouraging results in human clinical studies of cancer vaccines. These vaccines currently are available only to patient volunteers in research studies, and scientists have more hurdles to overcome before such treatments become standard practice. If all goes well, however, the first of these vaccines could receive federal approval within the next few years.

Unlike the scattershot effect of chemotherapy or radiation, which kills both healthy and cancerous tissue with significant side effects for patients, these vaccines are designed to destroy only malignant cells. These therapies don't offer a cure for patients and they don't prevent disease, like conventional vaccines. But experts hope that eventually these therapeutics may be powerful enough to destroy tumors and prevent recurrences of the disease -- without the debilitating side effects of current treatments.

For The Record
Los Angeles Times Wednesday March 19, 2003 Home Edition Main News Part A Page 2 National Desk 0 inches; 23 words Type of Material: Correction
Cancer vaccines -- In Monday's Health section, a graphic on cancer vaccines incorrectly referred to antigens as "antibody-producing." Antigens do not produce antibodies.
For The Record
Los Angeles Times Monday March 24, 2003 Home Edition Health Part F Page 8 Features Desk 0 inches; 20 words Type of Material: Correction
Cancer vaccines -- Last week's graphic on cancer vaccines incorrectly referred to antigens as "antibody-producing." Antigens do not produce antibodies.

"This opens up a whole new front in the war on cancer," says Dr. Heinz-Josef Lenz, an oncologist at USC/Norris Comprehensive Cancer Center in Los Angeles.

Chuck Bittick, for one, believes that an experimental colon cancer vaccine will help him beat the odds. Last June, Bittick, 63, was diagnosed with advanced colon cancer that had spread to his stomach, a condition that typically is fatal within two years. After surgery failed to remove all his cancer, he felt standard therapy didn't offer him much hope. So the Yorba Linda man volunteered for a national clinical trial in which a cancer vaccine was used in combination with chemotherapy. (Federal rules require that patients participating in research studies receive proven treatments before they receive experimental therapies.)

For four months, Bittick traveled to USC/Norris for weekly chemotherapy treatments and vaccine injections every six weeks. Within 12 weeks of beginning therapy last September, his cancer disappeared. "I thought my life was going to be over in a couple of years," says Bittick. "Now I just want to get back to surfing and being normal."

Researchers can't say for sure whether the vaccine eradicated Bittick's tumor. USC's Lenz, a researcher in the trial, said it is "very rare" to see that degree of tumor shrinkage in such a short time with patients given chemotherapy alone. "We think the vaccine worked synergistically with the chemo," he says.

Scientists are testing these treatments on patients with advanced cancers who have exhausted conventional treatments. But they also are hopeful that these therapies someday may be used to treat cancer patients at an earlier stage, when their immune systems haven't been depleted by fighting off the tumors, or ravaged by toxic chemotherapies.

"The most benefit from these therapies will probably be after surgery, to prevent a relapse," says Dr. Johannes Vieweg, a urologist and immunologist at Duke University in Durham, N.C., who is testing a vaccine for prostate and kidney cancer.

Scientists long have been intrigued by the idea of rallying a patient's immune system in the battle against cancer because they knew the immune system often eliminated small tumors on its own. "We occasionally see spontaneous remissions, particularly in melanoma and kidney cancers," says Vieweg. "The body can cure itself."

A smarter immune system

The scientific challenge was to teach the immune system to attack cancer cells. Since cancerous cells arise from the same tissue as normal ones, these malignancies evade detection by the immune system, which fails to recognize that the malignant cells are dangerous. Tumors also outwit the immune system by partially camouflaging their abnormal surface proteins, which makes them virtually invisible.

Consequently, the immune system had to be trained to distinguish mutant cancer cells from normal cells, and thus be spurred into action. Previous cancer vaccines, in which patients were injected with their own tumor cells, didn't work because only a fraction of the cells injected were able to survive.

"A lot of what we were doing five years ago we can throw out the window and attribute to naivete," says Dr. John A. Glaspy, an oncologist at UCLA's Geffen School of Medicine who has tested a vaccine on women with advanced breast cancer. "The immune system is very complex, but we have much more insight now into how it works. I'm optimistic that this time, we'll get a hit."

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