CHICAGO -- A large international study has shown for the first time that offering chemotherapy after surgery can modestly improve the survival of people with early-stage lung cancer. Even though the benefit is small, doctors say the finding is important, both because lung cancer is such a grim diagnosis and because it is so common. It is the No. 1 cancer killer, diagnosed in 1.2 million people around the world each year, and 85 per cent of victims die of the disease.

Chemotherapy after surgery is standard for treatment of breast and colon cancer. But until now, there has been no convincing evidence that it changes the course of lung cancer. Doctors do offer chemotherapy to patients, but the treatment is typically intended to ease symptoms rather than delay death.

The latest study, released yesterday, suggests lung cancer patients do have another treatment option, if their tumours are found early and can be removed with surgery. A follow-up round of chemotherapy improves their survival by several months.

Dr. Thierry Le Chevalier, who directed the study, said the results mean chemotherapy should be a routine option for patients who have surgery for early lung cancer.

"The benefit reported could prevent annually around 7,000 deaths worldwide," he said at a meeting in Chicago of the American Society of Clinical Oncology.

Several doctors agreed the results will have a major impact, although some questioned whether the change will be immediately embraced by all specialists.

"This will change the way lung cancer is treated," predicted society president, Dr. Paul Bunn, a lung cancer specialist at the University of Colorado.

Dr. Bruce Johnson of Harvard's Dana-Farber Cancer Institute said, "I will go home and discuss the study with patients and offer them this therapy."

However, Dr. Nassar Hanna of Indiana University noted that several smaller studies have tried and failed to prove that chemo does any good after lung cancer surgery.

"I don't think there will be an across-the-board change in practice, although many will be swayed," Hanna said.

The study was done on patients with non-small-cell lung cancer, by far the most common kind, which was confined to the lungs or had spread only to nearby lymph nodes. About a third of such patients are considered good candidates for surgery. Many cannot have surgery because they are not well enough to tolerate the operation, which typically takes out 20 per cent of the lung, or the disease has already spread to the lymph nodes in the neck and opposite side of the chest.

Doctors enrolled 1,867 patients at 148 hospitals in 33 countries. They were randomly assigned to get an operation alone or surgery plus chemotherapy. The treatment regimens included the drug cisplatin plus a variety of other standard chemotherapy medicines.

After five years, 45 per cent of patients getting chemotherapy were still alive, compared with 40 per cent of those getting only surgery. Average survival was 51 months for the chemotherapy patients and 44 months for the comparison group.

Cisplatin can have serious side-effects, including a drop in white blood cells that leaves patients open to infection.

Another study presented at the meeting yesterday raises the possibility that people taking cholesterol-lowering drugs to keep their hearts working smoothly may also lower their risk of cancer. Millions already take the drugs, called statins, and the latest work suggests they may be getting an unexpected benefit.