Hepatitis B, one of the world's leading killers and the leading cause of cirrhosis and liver cancer, can be cured in some cases and dramatically relieved in many others by treating patients with interferon, researchers reported yesterday.

According to a report in the New England Journal of Medicine, injections of synthetic copies of the natural protein can stop the hepatitis B virus from destroying the liver in almost half of the people who are chronically infected. One in 10 is cured, the virus being eradicated from the body.

Until now, there has been no treatment for the hepatitis B virus. While interferon clearly does not help everyone, having any therapy at all is considered to be an important step in controlling this infection.

"This is an encouraging result. All of us would feel a lot happier if we had a better treatment. This spurs us on to find that," said Baruch S. Blumberg of the Fox Chase Cancer Center in Philadelphia. He won the Nobel prize in medicine in 1976 for identifying the hepatitis B virus.

The latest research, conducted on 169 people at 12 hospitals, is the first large-scale comparison study of interferon for hepatitis B. It confirms smaller studies suggesting that the treatment often works.

Other studies have shown that interferon works against hepatitis C, another serious but less common variety of the virus. On Tuesday, an advisory panel of the Food and Drug Administration recommended interferon be marketed for hepatitis C.

Doctors said the latest study is big enough that physicians can use the results to predict how interferon will affect their patients if -- as seems likely -- it becomes the standard medicine for hepatitis B.

"We can be relatively sure what doctors will find in practice: Ten percent will be cured and 40 or 50 percent will be made better and their liver disease will be stopped in its tracks," said Robert P. Perrillo of the St. Louis Veterans Affairs Medical Center, the principal author of the study.

The results were published along with an editorial by Jay H. Hoofnagle of the National Institute of Diabetes and Digestive and Kidney Diseases.

"For now, interferon alpha offers the best hope" for treating chronic hepatitis B, Hoofnagle wrote.

Experts cautioned that the treatment should be used only for those with chronic infections who show signs of liver damage.

An estimated 1 million to 1.5 million people in the United States are long-term carriers of the virus, and at least half of them have liver disease. Worldwide, 300 million people, or 5 percent of the population, are chronically infected.

Hepatitis B is the chief underlying cause of liver cancer and cirrhosis. The World Health Organization ranks it as the ninth leading cause of death, just behind lung disease and well ahead of AIDS.

In his editorial, Hoofnagle described it as "the most important chronic viral infection affecting humans."

Hepatitis is likely to become the first major use for interferon. Isolating this natural disease-fighting substance was one of the early goals of genetic engineering. Interferon has turned out to be useful against a variety of diseases, but none is as common as hepatitis.

Although the FDA has not yet recommended interferon for hepatitis B, the drug is already on the market for other uses and physicians may legally use it any way they choose. Blumberg said some doctors already have begun prescribing it for this disease.

The interferon tested in the latest study is made by Schering-Plough, which financed the research. A similar product is made by Hoffman-LaRoche.