The trial began in 2002 and has involved more than 53,000 current and former heavy smokers 55 to 74 years of age. Individuals were randomized to undergo screening annually for 3 years with either CT or chest x-rays, and were then followed for another 5 years.

The results, which were reviewed by the trial's Data and Safety Monitoring Board on October 20, show a statistically significant difference in lung cancer mortality in the 2 groups, which led to the trial being halted. There were 354 lung cancer deaths among those who underwent CT screening and 442 among those who underwent chest x-ray (a 20% reduction).

"Lung cancer is the leading cause of cancer mortality in the United States and throughout the world, so a validated approach that can reduce lung cancer mortality by even 20% has the potential to spare very significant numbers of people from the ravages of this disease," Dr. Varmus explained.

"The results of this trial provide objective evidence of the benefits of low-dose helical CT screening in an older high-risk population, and suggest that if low-dose helical screening is implemented responsibly and individuals with abnormalities are judiciously followed, we have the potential to save thousands of lives," said Denise Aberle, MD, NLST national principal investigator.

"However, given the [strong] association between lung cancer and cigarette smoking, the trial investigators re-emphasize that the single best way to prevent lung cancer deaths is to never start smoking and, if already smoking, to quit permanently," she added.

Another finding from the study, which was not the primary end point, was a 7% reduction in all-cause mortality among people who were screened by CT, compared with those screened by chest x-ray. About 25% of all the deaths were due to lung cancer; the other deaths were related to causes such as cardiovascular disease, the NCI notes in its press release.

A fuller analysis of the results is being prepared for publication in a peer-reviewed journal in the next few months, according to the NCI.

Many Questions Remain

Approached for comment on the new finding, Michael Unger, MD, FACP, FCCP, who is director of the Pulmonary Cancer Detection and Prevention Program at Fox Chase Cancer Center in Philadelphia, Pennsylvania, pointed out that the actual data from the study have not yet been published. The results released so far "in essence" confirm the findings from the study by Dr. Henschke and colleagues, but many questions remain, he told Medscape Medical News.

"The most important is: Who is really at high risk?" he said. "Other questions include when and how long we should study the subjects." Then there is the issue of false positives, where the CT screen picks up lesions that are not lung cancer, he noted. Previous studies have reported high rates of false positives with CT screening for lung cancer, ranging from 25% to 70%.

"Basically, screening is not a test, it is a process involving correct diagnosis and most appropriate management," Dr. Unger said.

Source:  Medscape Medical News