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Cancer Study Finds Promise in CAT Scans for Smokers
Nearly everyone in the study with one of these "Stage I" tumors had them surgically removed, and 88 percent were alive five years later. Eight people who received no treatment -- the reasons were not specified -- died within five years.
"We have shown that when you diagnose it early that you can cure it," said Claudia I. Henschke of Weill Medical College of Cornell University, who headed the study. "We think this provides compelling evidence that you can save lives."
Some who disagree say the study had no controls -- no group randomly assigned to have no screening or to have some other kind of screening. Without a comparison group, it is impossible to say whether the outcomes of the smokers who received CAT scans was better.
It is not surprising that people whose lung cancers are found by a CAT scan survive longer than people whose tumors are found the usual way, after they cause pain or breathing problems. Screened patients receive diagnoses earlier and therefore will have the diagnosis for a longer time than someone whose tumor is found later, even if the two people die at the same time.
A study in the 1970s that screened smokers with chest X-rays every four months found exactly such contradictory results. The screened patients had a five-year survival rate of 35 percent, compared with 19 percent in the unscreened controls -- but the mortality rate from lung cancer was virtually identical in the two groups.
How could finding cancers when they are small ever be a bad idea?
Many experts say there is a chance that some small lung cancers will grow so slowly that they will never pose a health problem. This is true with some cases of prostate cancer and may be true of some cases of breast cancer, although the latter is less certain. Only a randomized controlled trial would be able to tell whether it is worth the risk, money, pain and emotional distress to find all small tumors and remove them.
Because many abnormal scans will lead to biopsies that involve sticking a needle into the lungs, "you need rather strong evidence that [screening] does what you think it does, namely reduces mortality," said Constantine Gatsonis, a biostatistician at Brown University.
The federal government is helping underwrite a $200 million study to try to do that. Gatsonis is one of the leaders of the National Lung Screening Trial, in which about 50,000 current or former smokers are being randomly assigned to receive three annual CAT scans or chest X-rays.
The third round of screening is almost finished, and results may be available in 2011 or 2012.