FRIDAY, March 25, 2005 (HealthDay News) -- CT scans can sometimes catch lung cancer early in longtime smokers, but a new study suggests their use makes no difference in overall survival rates.
On top of that, the researchers report, the screens often lead to higher medical costs, increased patient anxiety, and even unnecessary surgery in some cases. Their findings appear in the April issue of Radiology.
"On a positive note, we detected a fair number of early-stage cancers," said study author Dr. James Jett, a professor of medicine at the Mayo Clinic, in Rochester, N.Y. "However, we did not see any obvious evidence of a decrease in lung cancer mortality."
The study examined 1,520 men and women who were either current smokers or who had recently quit smoking, but were otherwise healthy. Study participants were aged 50 or older with a history of at least 20 years of pack-a-day smoking. Each person was given annual CT scans for four years; the researchers monitored the number and size of nodules found by radiologists who reviewed the results.
Overall, the scans detected 3,356 nodules deemed suspicious. Only 68 were actually cancerous, leaving 69 percent of the study participants with at least one false-positive diagnosis. Thirteen of the participants had a total of 15 surgeries for what turned out to be benign disease. The researchers noted that false-positive results carry "substantive financial, mortality, morbidity and quality-of-life costs" for patients.
Among the cancers that were diagnosed, 61 percent were in the early stage, compared to about 20 percent detected without the use of CT scans. "That is the good news," Jett said. "The hope is that by detecting cancer early we will reduce death."
Unfortunately, the research did not bear out that hope. Instead, while CT scan detection of early-stage cancers did go up, the number of late-stage cancers among the study group remained steady when compared with those detected in the Mayo Lung Project, a study conducted in the 1970s that used chest radiography (X-ray) as a screening tool.
"If you really had gotten a shift in picking up cancers early enough to cure them, then you should have seen fewer late-stage cancers," explained Norman H. Edelman, chief medical officer for the American Lung Association.
One possible explanation could be the detection of cancers that "a patient dies with, not from," the study authors said, a phenomenon called overdiagnosis.
"They picked up a lot of stuff that looks like cancer under the microscope," Edelman explained. "But these would not have gone on to be the cancers that kill people."
At this point, doctors still have no way of knowing which tumors will progress and which will remain relatively dormant, Jett said, and this can lead to patients being subjected to unnecessary treatments, such as surgery to remove the tumors. The average mortality rate with lung cancer surgeries is 3 percent to 5 percent, the researchers noted, so the procedure is not without risk.
The use of CT scans to detect all kinds of cancer in asymptomatic people has been a controversial issue in recent years. Specialty clinics tout the benefits of the scans for everything from heart disease to cancer, but the U.S. Food and Drug Administration -- which has approved the scans for general imaging purposes -- has not yet reviewed data to support these wider claims.
Edelman said that while the Mayo Clinic study is useful, the findings are not definitive. The study used an historical control group, instead of using a randomized study design, which is considered the gold standard of medical research. The National Cancer Institute is currently conducting a large, randomized trial that compares CT scans to chest X-rays in the diagnosis of lung cancer to see if there is a difference in patient mortality.
Lung cancer is the leading cause of cancer death in both men and women in the United States, according to the American Cancer Society. In 2005, there will be approximately 172,570 new cases of lung cancer diagnosed in the United States, and 163,510 people will die from the disease.
Meanwhile, the debate continues over whether the use of CT scans can save lives. Edelman said his association does not have a stated position on their use. And no professional radiological association endorses the use of CT scans to detect disease in seemingly healthy people, the researchers said.
More information
For more on lung cancer, visit, the American Lung Association.
