Frequent Lung Cancer Screening Benefit Goes Up in Smoke
The unexpected outcome led to a host of criticisms of the trial, with fingers pointing to the study design, the methods used, and the analysis. Critics argued that the researchers hadn't followed the men for long enough to see a benefit. Now, says Black, this very long-term follow-up of that study goes a long way toward clearing up the confusion.
By consulting the National Death Index, the team was able to assess the time and cause of death for more than 6,500 of the study participants. Even 20 years after the study, there was still "no significant decrease in lung cancer death with intense screening," says Black.
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."