CT Scans of Smokers Cut Lung Cancer Deaths by 20%
Trial Comparing CT With Standard X-ray Screening for Lung Cancer Halted Early
Lung Cancer Screening: Trial Details
Chest X-ray and low-dose helical CT scans (also called spiral CT) have both been used to find lung cancer early. But in the NLST, investigators were looking at which way of detecting lung cancer reduced death rates more.
The trial, launched in 2002, examined more than 53,000 former or current heavy smokers who had a history of at least 30 ''pack-years" but no symptoms or signs of lung cancer when they entered the trial.
Pack-years are computed by multiplying the average number of packs of cigarettes smoked per day by the number of years a person has smoked. A person who smokes a pack a day for 30 years, for instance, or 2 packs for 15 years, has a 30 pack-year history.
Participants were assigned randomly to either a low-dose helical CT or standard chest X-ray group and were given the same test annually for three years.
Lung Cancer Screening: Trial Results
When the researchers analyzed the results to date in late October, they found that the benefit of CT scans was clear.
The 20% reduction with CT scans is termed “very important," by Gastonis.
''What we are showing is, heavy smokers can see a benefit here [with CT screening] in mortality," he says.
According to the NCI, for every 300 participants screened with low-dose helical CT, one life has been extended.
A surprise finding is that the CT screening group also had a 7% reduction in overall death rate from any cause compared to the chest X-ray group, he says.
The ''false-positive" rate -- those screenings that detected an abnormality that upon further evaluation was not lung cancer -- was about 25% in the trial, Gatsonis says. In other studies of lung cancer CT screenings, the rate of abnormalities shown in former and current smokers ranged from 20% to 60%, with most of the abnormalities not turning out to be lung cancer.
The false positives, experts say, can cause anxiety and tests such as biopsies that could turn out to be negative.
But finding the cancer early with screening can extend life.