CHICAGO - Offering a glint of hope for treating a notorious killer, researchers found that a common chemotherapy drug can help pancreatic cancer patients who have undergone surgery stave off a return of the disease longer.

In the German study, the group receiving Gemzar, or gemcitabine, lived on average of 13.4 months without their cancer coming back. A comparison group that did not receive the drug lived without disease for 6.9 months.

The 6 1/2-month gain may look modest. And scientists said they have seen no difference so far in the overall survival rates between the two groups. But pancreatic cancer is such a rapid and efficient killer that the findings were still highly encouraging.

Pancreatic cancer has one of the worst chances of recovery of all types of cancer. Most patients are not diagnosed until the cancer has spread, and fewer than one in 10 patients are alive five years after diagnosis.

Only 20 per cent of newly diagnosed patients are good candidates for surgery, the best hope for a cure. And even then, the disease returns in the vast majority of cases.

The new findings, when considered along with preliminary results from a large U.S. trial reported last year, suggest that chemotherapy after pancreatic cancer surgery should at least include gemcitabine.

The study appears in Wednesday's Journal of the American Medical Association.

"This study says to me that gemcitabine can keep the disease at bay for a period of time after surgery," said Dr. Sunil Hingorani of the Fred Hutchinson Cancer Research Center in Seattle. But it also "underscores the essential incurability of the disease," he said. "If you wait long enough, the beast comes back."

The findings apply only to those patients who can have surgery -- just 6,000 to 6,500 patients a year in the United States. Those are the patients whose cancer was diagnosed before it spread beyond the pancreas.

Gemcitabine already is used to fight breast, lung and ovarian cancer. It is also used to treat inoperable pancreatic cancer. It costs about $2,800 a month and has relatively mild side effects such as fatigue and hair thinning.

Doctors disagree about the best treatment following surgery for pancreatic cancer. Some watch for the disease to recur before starting other therapies. Others recommend chemotherapy right away, or a combination of chemotherapy and radiation.

"Unfortunately, the majority of patients after surgery have their cancer come back," said Dr. Daniel Laheru of Johns Hopkins University School of Medicine, who was not involved in the study but specializes in pancreatic cancer. "That's why this study is important."

Unlike other cancers, pancreatic cancer appears to spread almost as soon as it appears, possibly because the pancreas is not as self-contained as other organs. Pancreatic cancer cells are also usually tougher to kill in a petri dish than other types of cancer cells.

The German researchers followed 354 patients after surgery for an average of 4 1/2 years. Some patients were chosen at random to get gemcitabine for about six months starting soon after surgery.

The researchers found that 74 per cent of patients receiving gemcitabine saw their cancer come back, versus 92 per cent of patients not getting the drug.

The patients were treated at 88 cancer centers in Germany and Austria.

Study co-author Dr. Hanno Riess of Charite School of Medicine in Berlin said the findings are changing practice in Europe, where most doctors previously had not used radiation or chemotherapy after pancreas surgery.

Worldwide, there are an estimated 232,000 new cases of pancreatic cancer annually. In the United States, it is the fourth leading cause of cancer death, claiming 32,300 lives last year.

The pancreas, located between the stomach and the spine, secretes enzymes that help digest food and hormones that maintain blood sugar levels.

Smoking and a family history of pancreatic cancer raise the risk of the disease. Eating more fruits and vegetables may reduce the risk.

Some of the study's authors reported financial ties to drug makers including Gemzar's manufacturer, Indianapolis-based Eli Lilly and Co. A grant from Lilly Deutschland supported the study, but the company had no say in its design or data interpretation, the researchers reported.