Screening heavy smokers with a computed tomography (CT) scan can catch tumors early and reduce deaths from lung cancers by 20 percent, according to a new clinical trial.

"Overall, this study provides strong evidence that older patients who are at high-risk of developing lung cancer could benefit from CT screening, and that's a significant finding," study researcher Dr. Claudine Isaacs, a director at the Lombardi Comprehensive Cancer Center at Georgetown University, said in a statement.

The National Lung Screening Trial study enrolled 53,000 men and women ages 55 to 74 starting in August 2002. Participants were required to have a smoking history of at least 30 "pack-years," which is calculated by multiplying the average number of cigarette packs smoked a day by the number of years the person has smoked. They were either current or former smokers who had no symptoms or history of lung cancer.

Researchers separated the people in the study into two groups: one received three annual low-dose helical CT scans — helical scans may give doctors a better view internal tissues than regular CT scans —  and the other received three annual standard chest X-rays.

The people in the study were screened when they first enrolled in the trial, and at the end of their first and second years on the trial, and then researchers followed up with them five years later.

Of the people who received the CT scans, 356 had died from lung cancer as of Oct. 20, whereas 442 people in the X-ray group had died of the disease, according to the study.

This means the scans reduced lung cancer deaths by 20.3 percent, the researchers said.

There are several disadvantages of using a CT scan, however, the National Cancer Institute said. The screening process produces false-positives, leading people to seek treatments for suspicious findings that turn out not to be cancer — an anxiety-inducing and costly endeavor.

There are also negative health effects of repeated exposure to radiation, as well as potential surgical and medical complications in people who may need extra testing to diagnose lung cancer.

A more complete analysis of the results is set to be released in the next few months, researchers said.

The study was published Nov. 3 in the journal Radiology.

This article was provided by MyHealthNewsDaily, a sister site to LiveScience.