The guidelines are based on a review of past studies which compared long-term health in smokers who underwent low-dose CT screening for lung cancer and those who got another cancer test or "usual care" instead.

Most of the evidence in favor of screening comes from a single large study known as the National Lung Screening Trial. That study found a 20-percent lower risk of lung cancer death among more than 26,000 people screened with low-dose CT annually for three years, compared to those who were tested with so-called chest radiographs instead.

But the combined prior research also suggested that in any round of CT screening, about one in five people will have positive results that require further testing, sometimes with invasive procedures -- although only one percent will actually have lung cancer.

"The trade-offs there are sizeable, even in the high-risk people," said Dr. Peter Bach, the lead author of the new review paper from Memorial Sloan-Kettering Cancer Center in New York.

"As you go down the risk range -- younger people, people who have smoked less -- because their chance of ever developing lung cancer is lower, the chance that they will benefit is also lower, and in some cases substantially lower," he told Reuters Health.

According to the new recommendations from the American College of Chest Physicians and the American Society of Clinical Oncology, annual screening should be offered to current and former smokers, age 55 to 74, who have smoked at least a pack of cigarettes a day for 30 years.

The screening recommendations don't apply to former smokers who quit more than 15 years ago, the researchers reported Sunday in the Journal of the American Medical Association.

Possible harms of lung cancer screening, they said, include the radiation associated with CT scans -- which over long periods of time may increase the risk of cancer itself -- as well as the unnecessary extra procedures and anxiety that come with a positive test that turns out to be a benign nodule.

Dr. James Mulshine, a lung cancer researcher at Rush Medical College in Chicago, said the new study may overplay the risks of screening compared to the benefits of catching potentially-deadly lung cancers early.

Currently, most lung cancers aren't caught until stage III or IV, and less than one in five people with a new diagnosis survives five years.

"Lung cancer screening is a big deal," Mulshine, also the vice president for research at Rush, told Reuters Health.

"Some people potentially will be harmed, and there's even the chance some people will die (because of complications from screening). But that's also the case of flu shots… and driving to the doctor's office."

He also suggested CT scans and other procedures are becoming safer over time, lowering the chance of screening-related harm.

Mulshine, who wasn't involved in the new study, said it's "very reasonable" for current or former heavy smokers to have a discussion with their doctors about the benefits and risks of lung cancer screening.

And any screening that is done, he said, should be combined with advice on how to quit smoking and referrals to smoking cessation programs for people who haven't yet kicked the habit.

‘NOT A NO-BRAINER'

According to the Centers for Disease Control and Prevention, close to 160,000 people in the United States died from lung cancer in 2008, the most recent year with available data. Nationally, more men and women die from lung cancer than any other type of cancer.

Screening for lung cancer nodules runs about $300.

One of the original studies suggesting CT scans could prevent deaths from lung cancer was later criticized over ethical issues with how the research was conducted.

Since then, the National Lung Screening Trial has been the largest gold-standard study to evaluate low-dose CT screening -- and the only one to convincingly show a benefit, the researchers reported. Two smaller studies analyzed by Bach and his colleagues included fewer than 5,000 participants each and didn't find any difference in deaths with screening.

Bach said most people who get screened for lung cancer won't benefit from it -- because they don't have cancer -- and also won't suffer any side effects.

People at high risk of cancer, he said, should "weigh the benefits and risks" of screening based both on their own chance of cancer and their values.

"This is not a no-brainer in any sense," Bach said.

"We think on balance it's worth it enough that it would be a reasonable decision for an individual (at high risk) to be screened, but I think different people value the risks and benefits differently."

SOURCE: bit.ly/LuIyzk Journal of the American Medical Association, online May 20, 2012.

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