A years-long study that compared methods of detecting lung cancer is ending early because the researchers believe they have identified a method that can reduce deaths by 20 percent.

Lung cancer is the leading cause of cancer-related deaths. It killed 159,390 people in 2009, according to the National Cancer Institute – more people than breast, prostate, colon and pancreatic cancer combined.

Not all lung cancer is a result of smoking. But with 90 million current and former smokers around the nation at higher risk of developing lung cancer, finding a way to diagnose and treat them has been a priority at the National Cancer Institute, which initiated the study.

The randomized clinical trial, which began in 2002 with 53,000 current and former heavy smokers, found that spiral computed tomography (CT) scans are better than standard X-rays. Thirty sites were used to test the patients for lung cancer, including Johns Hopkins in Maryland. A University of Maryland oncologist also helped verify the study results.

Now, most lung cancers are detected when there are symptoms, often after it has spread outside the lung in up to 30 percent of cases, according to the National Cancer Institute. The CT scan, first used in the 1990s, is better at finding small cancers before they have spread.

While the CT scans were found to be more effective in finding cancer earlier, there were drawbacks. It’s more costly and not covered by most insurance or Medicare. It can have a higher rate of false positives, which could lead to more unnecessary procedures. And there’s more radiation to the patients, itself a cancer causer.

The study was supposed to last 10 years, but a body examining the study said there was enough evidence to stop and issue findings and publish the data in a peer-reviewed journal.

According to Dr. Harold Varmus, NCI Director, during a press conference today, “Lung cancer is the leading cause of cancer mortality in the U.S. and throughout the world, so a validated approach that can reduce lung cancer mortality by even 20 percent has the potential to spare very significant numbers of people from the ravages of this disease. 

He added, "But these findings should in no way distract us from continued efforts to curtail the use of tobacco, which will remain the major causative factor for lung cancer and several other diseases.”