CHICAGO (Reuters) - Should smokers and ex-smokers get an annual screening test for lung cancer? With experts divided, patients may be left on their own to decide.

A panel of experts on Friday showed that the issue may not be resolved any time soon, leaving doctors and patients to weigh the risks and benefits.

Currently, a large clinical trial is underway to see if using advanced X-rays called spiral CT scans will improve the odds for people to survive lung cancer.

The researcher who has led the drive for screening told a meeting of the National Lung Cancer Partnership in Chicago that the study is flawed, and urged public health experts to recommend annual screening for people at risk for lung cancer.

“Screening using low dose CT reduces death from lung cancer. It finds it early and early treatment is better than later treatment,” said Dr. Claudia Henschke of the New York-Presbyterian Hospital/Weill Cornell Medical Center.

Henschke said the lung screening trial sponsored by the National Cancer Institute -- which aims to settle the debate over whether the screening saves lives -- is unlikely to prove anything because it will not screen patients for long enough.

The screening is scheduled to be completed in 2009.

However other experts say the trial is necessary to prove benefits of the more sensitive screening that could result in patients undergoing unnecessary procedures by identifying spots that do not pose a risk.

Henschke last fall published a study in the New England Journal of Medicine that supports the argument that yearly computed tomography or CT scans could have a dramatic impact on lung cancer death rates.

In 1999, she and other researchers found that spiral CT scanning could spot 85 percent of small lung tumors while they could still be surgically removed.

Currently, when lung cancer is detected, the disease has already spread outside the lung in 15 percent to 30 percent of cases. Once it has spread, it is rarely curable.

Dr. Denise Aberle of the University of California-Los Angeles, who is a lead researcher in the screening trial, said the study -- which is to be completed in 2009 -- is needed to determine whether the benefits of screening outweigh the risks.

“The benefit of screening hasn’t been proven,” she said in an interview. “It’s important the public understand that.”

CT scans can detect a number of problems that may or may not pose a risk, Aberle said.

“Most of the findings will not be clinically significant, yet they convert the ostensibly healthy individual into a patient,” Aberle said.

Some studies have shown the scans result in a tenfold increase in operations.

Lung cancer is the leading cause of cancer-related deaths. It kills 164,000 Americans a year and 1.3 million people a year globally.