TUESDAY, March 6, 2007 (HealthDay News) -- CT scans for lung cancer may increase the rate of diagnosis and treatment of the disease, but they may not help lower the numbers of patients with advanced lung malignancies or related deaths.
So concludes a new study in the March 7 Journal of the American Medical Association. The new findings are in contrast to an earlier trial, the International Early Action Lung Cancer Program (I-ELCAP), which indicated that spiral CT screening could prevent 80 percent of lung cancer deaths.
The authors of that study had argued that a large randomized trial of CT screening be stopped, because the effectiveness of the method had already been proven.
The authors of the new study disagree.
"We believe this method is not proven and should not be used broadly until a definitive randomized trial has been completed. That's in progress and won't be finished until 2009," said Colin B. Begg, senior author of the study and chairman of the department of epidemiology and biostatistics at Memorial Sloan-Kettering Cancer Center in New York City. The upcoming trial "is an extremely well-funded study which should settle this question once and for all," he said.
Another expert agreed that more and better study is needed.
"It's an important issue, because lung cancer kills more people than any other cancer, and our ability to do much about it, unless it's caught very early, is very bad. So early detection is a big deal," said Dr. Norman Edelman, chief medical officer for the American Lung Association.
"But you just have to study each proposal, because you never know exactly how it's going to work out," he added. "It's only a real-life study [such as the currently ongoing National Cancer Institute trial] that can solve the issue."
Lung cancer remains the leading cause of cancer deaths. Because of a lack of adequate detection methods, malignancies are often diagnosed at an advanced stage, limiting treatment. While the five-year survival rate among patients with stage I lung cancer is about 70 percent, it is only 5 percent among those with stage IV disease. Unfortunately, stage I lung cancer diagnoses are rare.
In their analysis, Begg and his colleagues revisited three prior studies involving a total of 3,246 asymptomatic current or former smokers who underwent annual CT lung cancer screening, beginning in 1998.
Individuals screened with CT were three times more likely to be diagnosed with lung cancer and 10 times more likely to undergo surgery for the disease, they reported.
But CT screening did not appear to cut the risk that the disease would become advanced and end in death.
"This doesn't contradict previous studies," said Edelman. "Previous studies show that CT spiral can find more lung cancers at an earlier stage. This study says that, despite that, there's no impact on outcome."
The differences between this and the previous study seemed to hinge on how the authors interpreted their findings, Begg said. "Our results are perfectly consistent with their results, but we interpreted the results differently," he said. For example, the prior studies looked at survival -- how long people lived after their lung cancer diagnosis -- whereas this trial compared the actual number of deaths.
"We believe, as do most experts in cancer prevention, that in order to assess properly a screening intervention, you have to measure the number of deaths from cancer in relation to all of the people who were screened," Begg said. "That is the mortality rate. And when we do that and benchmark it against the expected death rate in people of this age and smoking history, we find there's no difference."
"This is important, because it comes from an institution that's been promoting this stuff," Edelman said. "But they said that when they look at mortality, they can't show a positive effect."
The new results call into question the advisability of operating on these early cancers, if most of them are unlikely to progress rapidly. Surgery on its own can carry significant risks, Begg noted.
"Our study, although preliminary, provides no evidence whatsoever that screening is reducing mortality," he said.
For more on lung cancer, visit the U.S. National Cancer Institute.