At an American Cancer Society briefing here on key developments in research, Dr. Harinder Garewal of the Veterans Affairs Medical Center in Tucson, Ariz., said that early human studies of the technique have shown it to be safe and able to shrink tumors in half of the 82 patients tested at centers in the United States and Europe.

Treated tumors disappeared in 39 percent of patients. "These are tremendously encouraging results," said Garewal. It would be unusual to encounter tumor shrinkage in even one or two patients from a similar group given standard chemotherapy treatment.

The focus of the research is on head and neck tumors, grotesquely disfiguring lesions that can grow to the size of lemons and suffocate victims by blocking their airways. Ranked the sixth most common in the world, head and neck cancer strikes 42,000 Americans a year and kills up to 15,000 annually.

Even though the treatment has spared many patients surgery and further discomfort, patients in the early studies of this cancer treatment had their disease spread so extensively throughout their body that it is unlikely the treatment would reverse the course of their illness.

Key to the experimental treatment is a collagen-derived substance that has an unusual characteristic: It is almost liquid at room temperature but thickens to a honeylike viscosity at body temperature.

Garewal mixes the chemotherapy drug cisplatin and epinephrine - also known as Adrenalin - into the substance and injects it directly into the tumor. The collagen thickens and stays at the site for several days before it breaks down naturally. Adrenalin constricts blood vessels to further reduce the dispersion of the drug.

Direct injection of chemotherapy drugs to solid tumors has been done before. "The problem is that if you just take a syringe and stick it in the tumor, the drug is gone from there in a few seconds. It just won't stay there," said Garewal.