Cancer researchers at Johns Hopkins University said this week they have found "the first effective treatment" for advanced liver cancer, a disease that is almost always fatal when caught too late to be surgically removed.

The work of the Hopkins group and other researchers on antitumor antibodies ushers in "a new era" in cancer treatment, because it will allow doctors to combine the use of antibodies with drugs and radiation to increase chances of curing the disease, said Dr. Gregory Curt, deputy director of the National Cancer Institute's division of cancer treatment.

Experts in cancer treatment at the National Cancer Institute said the Hopkins team's results, which have been accepted for publication in the Journal of Clinical Oncology, appear to represent an impressive advance in treatment of one of the most lethal forms of cancer.

The Hopkins group's "results in hepatoma," or primary liver cancer, are "a lot better than anything I've ever treated," said Dr. Eli Glatstein, chief of radiation oncology at the institute.

"In this disease, in patients with diffuse hepatoma, the five-year survival rate is zero," Curt said. "The fact that it works at all is very encouraging."

The treatment employs radioactive isotopes attached to antibodies, proteins that bind to a substance found in the cancer cells, thus delivering destructive radiation directly to the tumor, according to Dr. Stanley E. Order, director of radiation oncology at Johns Hopkins Hospital.

Tried on 104 patients with inoperable liver cancers, the new treatment shrank tumors by 30 percent or more in 50 patients and produced total remission in seven, Order said. In contrast, conventional treatments produce some response in 15 percent of cases, he said.

Order cautioned that the new treatment is far from a cure for most patients and "still not as good as it should be. I only consider this a beginning."

An estimated 13,400 cases of cancer of the liver and bile ducts occur annually in the United States, with 10,400 deaths, according to American Cancer Society statistics. Curt said the survivors are patients whose tumors are caught soon enough to be surgically removed.

He said liver cancer appears to be caused by chronic inflammation of the organ, as occurs in alcoholic cirrhosis and chronic infectious hepatitis. He said the highest rates of liver cancer occur in China and other parts of eastern Asia, where hepatitis B rates are very high.

In the technique used at Johns Hopkins, animal antibodies are produced against ferritin, an iron-storing protein present in liver cancer cells and some other tissues. The antibodies are then "labeled" with radioactive iodine or other isotopes. When injected into the bloodstream, they bind to ferritin in the tumor cells and continuously deliver a low dose of radiation.

Order said seven of his patients, including one diagnosed nearly four years ago, are in total remission, with no evidence of cancer left in the liver. Others have reached a "plateau," with tumors that seem to be neither growing nor shrinking, he said.

He said the median survival among the treated patients so far is about eight months, double the median survival time for patients treated conventionally.

The exact mechanism of the treatment is not fully understood. He said the results can only be partially explained by the efficiency of the direct, continuous radiation dose.

"There has to be something else," Order said. He said the injected antibodies may help trigger the body's immune system as well as delivering radiation to the cancer.