Frequent Lung Cancer Screening Benefit Goes Up in Smoke
But shouldn't early detection, and the resulting treatment, help lower the number of lung cancer deaths? Not necessarily, the experts now agree, and here's why:
Overdiagnosis is the most likely explanation, says Marcus. "When you go looking for things, you find them." Intense screening reveals tumors you never would have picked up otherwise. They might be innocuous tumors that would probably not kill you before you died of other causes. If such a tumor is found, and treatment begun, the cure could end up causing more pain, and being more deadly, than the undetected cancer ever would have been, she says.
Black agrees with the theory. "I think there definitely is a similar component in lung cancer to what's seen in prostate cancer," he tells WebMD. "Some tumors grow rapidly and are lethal, some grow slowly and don't need to be treated." With more screening, more slow-growing cancers are identified. "While some people may be helped by increased screening, in the group overall there was no benefit. In fact, more people were harmed than helped."
Not only will this information help guide future research, it is an important lesson for both doctors and patients. "In the real world, you almost never identify an individual who has been overdiagnosed," says Black. You only appreciate the harm, he says, with the findings of a large study.
While Black does not think that lung-cancer screening should be eliminated outside of clinical trials, he does suggest that doctors "disclose the possibility of being diagnosed with something that [isn't fatal] -- especially if the patient is a smoker and is likely to die of something else before they die of the cancer."
Marcus concurs. Down the road, she says, markers in the blood and sputum may offer more precise lung cancer screening than X-rays, or even the latest imaging technology -- spiral CT. For now, however, "doctors should be educating patients about the pros and cons of screening."
According to Marcus, an ongoing trial of X-ray screening in prostate, lung, colorectal, and ovarian cancer, may yet show a benefit. This time, she says, they are comparing chest X-ray with no screening at all, in both smokers and nonsmokers.
But even if that trial is positive, the best way to improve your chance of surviving cancer free is to quit smoking. "It would be far more beneficial for a person to stop smoking than to be screened," says Black. "The increase in life expectancy is much, much greater from quitting than it would ever be with screening."
The paper and the editorial both appear in the Journal of the National Cancer Institute.