By Sue Rochman
How do we know if screening tests save lives?
By Sue Rochman
We have come to believe in, perhaps some would even say put faith in, cancer screening tests. We diligently follow our doctors’ recommendations, schedule our annual exams, and then cross our fingers that all will be well. And why shouldn’t we? Who doesn’t know someone who sings the praises of the mammogram, Pap smear, PSA test or colonoscopy that they believe saved their—or a loved one’s—life? Who wants to harbor the regret that if only the cancer had been found early, things might be different today?
But how do we know which screening tests really work?
For Claudia Henschke, there is no question that annual lung cancer screening can save lives. In fact, she could fill a room with her apparent evidence: more than 400 women and men who are alive today, she says, because they had an annual CT scan that detected an early stage lung cancer.
Like so many other cancers, lung cancer doesn’t cause any noticeable symptoms at first. As a result, most people are not diagnosed until they have late-stage disease. Henschke, a radiologist at Weill Medical College of Cornell University in New York City, believed that CT exams could change that. In 1993, she began to enroll people at risk for lung cancer in a study, now known as the International Early Lung Cancer Action Program (I-ELCAP), which screened each participant annually with a CT scan.
An estimated 180,000 people are diagnosed with lung cancer each year in the U.S., the leading cause of cancer deaths in the country. And most face a poor prognosis: The overall five-year-survival rate is a grim 16 percent. So when Henschke and her colleagues published a study in the New England Journal of Medicine in October 2006 showing I-ELCAP participants had an estimated 10-year survival rate of 80 percent, one might have expected the cancer community to herald Henschke a superstar.
But that’s not what happened. Instead, Henschke has had to defend her work time and time again. The problem: Not everyone believes she has shown that annual CT exams save lives. And that’s because, when you begin to study a cancer screening test, what you think you see is not always what’s there—even Henschke’s roomful of cancer survivors.
Not So Fast
Barnett Kramer, an oncologist who is the director of the Office of Medical Applications of Research at the National Institutes of Health, would like nothing more than to see a screening test that would reduce the death rate from lung cancer. But when he looks at Henschke’s data, that’s not what he sees.
Research studies are divided into four sections: background, methods, results and conclusions. The conclusions give the bottom line: good or bad, yes or no. That’s what most people want to know. And it’s what most physicians want to know, too.