The Risks of Cancer Screening
With More Cancer Screening and Earlier Testing, Overtreatment on the Rise
Living With Uncertainty: The Limits of Science
Short of a cure, perhaps the greatest unmet need in cancer research is to find tests that tell us which tumors need to be treated.
"What we need to do as scientists is to find better tests. Tests that are more specific, cheaper, not expensive, and five to 15 years later show we are detecting more cancers and less people are dying," Gluck says. "But if the tests detect the same number of cancers and same numbers of people are dying, a test is not effective."
Nearly all patients treated for screening-detected cancers believe their treatment cured their cancer and saved their lives. But many if not most of them never needed to be cured at all. They were overdiagnosed and overtreated.
"Unfortunately right now we are left with diagnosing a large number of people without precise enough knowledge to spare those who don't need to be treated," Kramer says. "And because cancer is such a fearsome disease, we often feel that patients can't tolerate going untreated."
Prostate cancer offers a good example. According to the U.S. Preventive Services Task Force (USPSTF), "A large majority of the men who are being treated would do well without treatment." Yet in the U.S., 90% of these men opt for treatment.
"We have a culture of treating cancers aggressively, but we know all those men don't need to be treated," Kramer says.
Another example is the most feared form of skin cancer: melanoma. Melanoma rates have gone up since the late 1980s. Most of the increase is in early cancers detected as skin-exam screening became more common. But late-stage melanoma cases didn't decline, Kramer says. Neither did the death rate.
Brawley agrees. "I cannot quote a study showing that melanoma screening definitely saves lives," he says. "We cure some melanomas that don't need to be cured."
Nobody wants to live with cancer. Nobody wants to be overdiagnosed or overtreated. It's just that we want -- need -- answers that medical science does not yet have.
"What we really need is a 21st century definition of cancer so we can move away from 20th century screening and diagnosis using an 1840s definition of cancer," Brawley says.
There are limits to science, says Susan G. Fisher, PhD, professor and chair of public health sciences at the University of Rochester, N.Y.
"People are uncomfortable and concerned because they think we are recommending less screening in some groups," she says. "The message for the public is that science is hard. As we get more and more information we get smarter about our advice. The most recent evidence says that in groups at low risk, we are creating more problems than benefits with early screening."