Older people with lung cancer shouldn't routinely receive radiation because it doesn't help them live longer, a new U.S. study finds.

People with lung cancer that has spread to lymph nodes in the chest usually have surgery to remove the tumours. What's less clear is whether their survival improves if they also get radiation after the surgery to reduce the chance of recurrence as suspected.

In this week's online issue of the journal Cancer, researchers say for older people, the answer is often no.

"Our results show that we need more information about the potential benefits of radiation therapy before it is used routinely to treat this subset of lung cancer patients," said study author Dr. Juan Wisnivesky of Mount Sinai School of Medicine in New York City.

In the study, Wisnivesky and his co-authors analyzed a registry of Medicare records from 1992 to 2005. Most of the patients were over age 70.

Of the 1,307 advanced cases of lung cancer, 710 patients, or 54 per cent,received radiation after their surgery. They were not more likely to survive than those who didn't receive radiation, the researchers said.

Wisnivesky's team took patient characteristics, tumour size, type of surgery and complications into account. But the authors acknowledged it isn't possible to compare the two groups perfectly since individual treatment decisions vary.

For the type of lung cancer in the study, about 20 per cent to 30 per cent of patients survive five years after diagnosis.