CT for lung cancer may do more harm than good

Annual screening for lung cancer using computed tomography (CT) can help detect the disease at its earliest, most curable stage, but it does not reduce mortality from the disease and could actually result in more harm than good, according to a new study.

"What we're finding with CT screening are more early-stage cancers. That could be good news - finding cancers that we'd otherwise find at a late stage," Dr. Stephen J. Swensen from the Mayo Clinic in Rochester, Minnesota, said in a statement. "However, a number of these are probably non-lethal or slow-growing cancers that the patient would likely have died with not from. Other cancers were so aggressive that early detection with CT did not make a difference," he added.

While recent studies have focused on the benefits of early detection with CT, Swensen and colleagues looked more closely at the possible negative impact of CT screening. In the April issue of the journal Radiology, they report results in 1,520 subjects who had undergone five annual CT examinations. These subjects were aged 50 years and older and had smoked for more than 20 pack-years.

Altogether, 3,356 uncalcified nodules were identified in 1,118 (74 percent) participants. The false-positive rate - that is, the percentage of nodules that proved to be benign at surgery or by observation - ranged from 92 percent to 96 percent.

There were 68 primary lung cancers detected in 66 participants, and nine deaths from lung cancer occurred. According to the authors, this rate was not significantly different from that observed in a study examining the benefit of annual radiography, although the current trial detected a larger proportion of early stage lung cancers. There was no decrease in advanced stage cancers.

Swensen and colleagues point out that interventions for benign nodules are costly, resulting in significant illness, death and decrements in quality of life.

"That's a big price to pay if it's a benign nodule," Swenson said.

"While there is still reason to hope that early detection of lung cancer with CT may save lives, our results lead us to be very cautious, because there's a chance that we may be doing more harm than good," he said.

SOURCE: Radiology April 2005.