NEW YORK - X-ray screening for lung cancer may not save many lives, a team of U.S. and Italian researchers reported in a study that adds to a growing debate.

A type of X-ray called spiral CT, or computed tomography, can find lung cancer tumors when they are very small and easily removed, but it is not clear whether it is worthwhile to screen smokers and other people at high risk.

"Screening for lung cancer with low-dose CT may increase the rate of lung cancer diagnosis and treatment, but may not meaningfully reduce the risk of advanced lung cancer or death from lung cancer," Dr. Peter Bach of the Memorial Sloan-Kettering Cancer Center in New York and colleagues concluded in their report.

Bach's team studied 3,200 people screened for lung cancer at three centers in the United States and Italy and followed them for four years on average.

"There were 144 individuals diagnosed with lung cancer compared with 44.5 expected cases (without screening)," they wrote in their report, published in the Journal of the American Medical Association.

They said 38 people died and that was what would have been expected without screening.

"Until more conclusive data are available, asymptomatic individuals should not be screened outside of clinical research studies," they advised.

Lung cancer is by far the biggest cancer killer in the world. It kills 1.3 million people a year globally, 160,000 in the United States and 334,800 in the European Union.

One reason it is so deadly is that lung cancer does not usually cause symptoms until it has spread.

BUYING TIME

One big study published in the New England Journal of Medicine in October showed that annual CT scans could buy lung cancer patients at least 10 years and perhaps longer.

Dr. Claudia Henschke of the New York-Presbyterian/Weill Cornell Medical Center led that study and believes it shows the benefits of screening smokers with an annual CT scan.

She believes Bach's study confirms what she found.

"I find that his data really are, instead of being in stark contrast to, they really support our data," Henschke said in a telephone interview.

"They are just reported in negative ways." She also questioned some of Bach's analytical methods.

But Dr. David Johnson of Vanderbilt University in Tennessee, a lung cancer expert and former president of the American Society for Clinical Oncology, said the Bach study showed just how confusing the issue still was.

He said it was important to have researchers go through the scientific process of doing research, and having other researchers question it. "I think these data interject the appropriate note of caution," Johnson by telephone.