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Screening allows us to look under the water, at the tumors that haven't yet become symptomatic. We assume they will eventually cause symptoms, but increasing evidence suggests that's not always the case. Evidence from autopsies, for instance: In one study, postmortem exams showed that nearly 9 percent of women of all ages who died of any cause other than breast cancer had undiagnosed DCIS. Among women from Denmark, where mammography is not as common as it is here, a whopping 39 percent of middle-aged women who died of other causes had undetected breast cancers. Similarly, says outcomes researcher Dr. Welch, a 1989 study found that 60 percent of men over age 60 have undetected prostate cancer -- yet only about 3 percent of deaths in men are due to prostate cancer.
So screening tests raise red flags about cancers destined to loll about quietly, causing no problems. But there's more. They also blare the alarm about cancers that would actually go away on their own -- because, in fact, some cancers simply disappear.
Brandon Connor, now age seven, was suspected of having cancer even before he was born. It had been a difficult pregnancy, and Brandon's mother, Kristin, then 35 and a lawyer in Atlanta, was undergoing regular ultrasounds. One of the tests picked up what looked like a tumor on Brandon's spine. Doctors made a tentative diagnosis of neuroblastoma, a nervous system cancer.
Neuroblastoma comes in two forms, one of which is deadly. But there was no way of knowing if Brandon's tumor was indeed a neuroblastoma, much less whether it was dangerous, without doing a biopsy, and its location made that risky. The Connors opted instead to keep a close watch to see if the cancer grew; the doctors said Brandon's tumor should regress within his first year if it was going to. It didn't, and by the time Brandon was two years old, he'd undergone more than a dozen MRI scans.
Finally, the doctors advised the Connors to go ahead with surgery. The day before the operation, though, the surgeon ordered one last imaging test. The neuroblastoma was gone. "We couldn't believe it," says his mother. Today, physicians know that many neuroblastomas regress on their own during infancy or early childhood.
"People kept telling us, 'Thank God they found it on the ultrasound,'" Kristin Connor says. Looking back on the years of worry, she adds, "In hindsight, I'd say it was more like a curse."
The Damage Screening Can DoForget the fact that unnecessary therapies for cancer are a tremendous drain on our health care budget, already strained to the breaking point. "Many oncologists would probably tell you that they've had patients who suffered serious side effects, even death, from treatment that they might not have needed," says William C. Black, MD, a professor of radiology at Dartmouth-Hitchcock Medical Center. No one intentionally prescribes unnecessary treatment, of course. But it's often difficult to know if a patient really needs to be treated, so the tendency is to be aggressive, just in case.
Treatment can exact a profound toll. Take the case of George Brown. At 75, Brown was still a practicing lawyer in Denver last year when he was diagnosed with prostate cancer. His doctor prescribed Lupron to block production of testosterone (which many prostate tumors need in order to grow). "I didn't realize that Lupron was chemical castration," says Brown. "I was extremely depressed. I was having hot and cold flashes. I cried at everything." Radiation therapy damaged his rectum and left him with little control of his bladder or bowels. He is now facing another round of a different testosterone-blocking drug.
Despite his troubles, Brown believes his care was lifesaving. And there's no way to know in any particular case. But the fact is that most men diagnosed with this cancer have invasive therapy, even though statistics say that many men could safely choose "watchful waiting": getting PSA tests to monitor the cancer and treating it only if it begins to grow rapidly.
Does Screening Save Lives?For many people, even serious side effects like the ones Brown suffered would be worth putting up with if the treatment reduced their risk of dying of cancer. That's the point of getting screened, isn't it? Yet only one cancer screening test, the venerable Pap smear, has truly slashed the risk of death. Between 1955 and 1992, according to the American Cancer Society, Pap smears cut the death rate for cervical cancer by 74 percent, and deaths have continued to decline each year.
But no other test has had such a powerful effect. The PSA test has been widely used in the United States since the late 1980s, but it's not clear that it's had a big impact on the death rate for prostate cancer. Between 1975 and 2005, the latest year for which statistics are available, the death rate dropped from 31 per 100,000 men to 24.6. That's a real decline, but many experts doubt that PSA testing deserves all the credit -- especially given what happened during a "natural experiment" in Seattle and the state of Connecticut in the late 1980s.
Medicare patients in Seattle were five times more likely than those in Connecticut to get PSA testing between 1988 and 1990 and were also more likely to have surgery and radiation for prostate cancer. But when researchers followed up through 1997, they found the Seattle men were just as likely to die of prostate cancer.
"Prostate screening seems to make sense," says Nortin M. Hadler, MD, a professor of medicine at the University of North Carolina at Chapel Hill and the author of Worried Sick: A Prescription for Health in an Over-treated America. "If only it worked."
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