Genetic Radiotherapy Packs Powerful Punch

New treatment combo shrinks tumors in animals

TUESDAY, July 16, 2002 (HealthDayNews) -- A combination of genetic therapy and radiation to shrink malignant tumors is showing promise in animals, say scientists who hope human cancers can one day be treated the same way.

Researchers at the Virginia Commonwealth University found that injecting cancer cells with a virus made them more sensitive to radiation and they were more easily killed by radiation than were cancer cells subjected to radiation alone.

As a result, the tumors in animals that received the genetic radiotherapy did not grow as much as the tumors in animals that received only radiotherapy did, says Paul Keall, an assistant professor of radiation oncology at the Virginia Commonwealth University.

"The virus was injected into cancer cells with a syringe mechanism and was able to block the normal pathways of the cancer cells, inhibiting [the tumor's] ability to repair itself," he says. When subjected to radiation, the newly vulnerable cancer cells were easier to kill, he adds.

Keall presented a paper on the research yesterday at the annual meeting of the American Association of Physicists in Medicine in Montreal.

In the fall, Virginia Commonwealth will begin clinical trials on humans to see if the animal results can be replicated, Keall says.

"We're trying to apply the same test to humans, but the biological response of every animal is different. There is great biodiversity, both between different species and amid each species, so you can never test a result until you apply it specifically to each group," he says.

If the tumor reduction were to be the same in the humans as it was in the animal studies, he adds, a statistical analysis of present cancer data shows the cancer cure rate could be 15 percent higher if people had the combination therapy instead of just radiation.

"Gene therapy alone and radiation alone are both somewhat effective, but put together there's a synergy to the effect. The sum is greater than its parts," says Michael G. Herman, head of physics in the radiation and oncology department of the Mayor Clinic.

Herman organized a symposium on the topic of combination therapies for the meeting, but he emphasizes it will be some time before this science can be used on cancer patients.

"It's good for people to become a little bit educated about the possibilities for combination therapies, but it's important to realize that it requires a lot of funding and time for these things to evolve," he says.

What To Do

For good information about the gene therapy, you can visit The Human Genome Project. An explanation of how radiation is used to treat cancer can be found at the National Institutes of Health.

SOURCES: Paul Keall, Ph.D., assistant professor, radiology and oncology, Virginia Commonwealth University, Richmond, Va.; Michael G. Herman, Ph.D., head, physics, radiology and oncology department, Mayo Clinic, Rochester, Minn.; July 15, 2002, presentation, American Association of Physicists in Medicine annual meeting, Montreal
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