A procedure for freezing tumors offers new hope for victims of liver cancer - one of the deadliest forms of the disease - and may also be useful against prostate cancer, a scientist says.

Of 30 liver cancer patients who underwent the procedure, six are disease-free, said Dr. Gary Onik of Pittsburgh's Presbyterian Hospital. His work was reported Tuesday at the 76th Scientific Assembly and Annual Meeting of the Radiological Society of North America.The technique, called cryosurgery, can destroy tumors next to major blood vessels without destroying normal tissues nearby, Onik said.

Onik and colleagues also have tested the ultrasound-guided probes that freeze cancerous tumors with liquid nitrogen on seven prostate cancer patients. Of those patients, no complications have resulted, Onik said.

Onik said the technique can benefit patients whose cancer is caught before it affects the whole liver. He said radiation and chemotherapy are ineffective against liver cancer.

"Everybody we worked on by definition couldn't be helped any other way," Onik said.

The patients who are disease-free have survived an average of 29 months, with the longest five years, he said. Survival for the other patients has averaged 22 months, and two whose cancer has come back are still alive, he said.

The projected survival among comparable liver cancer patients who don't use cryosurgery is six to nine months, Onik said.

Dr. Andrew Gage, deputy director of the Roswell Park Cancer Institute in Buffalo, N.Y., said Onik's technique offers hope to patients who otherwise would be lost.