November 22, 2009 in Nation/World

Routine cancer screenings draw increasing scrutiny from experts

Karen Kaplan Los Angeles Times
 

Varied results

Routine cancer screening is designed to catch tumors at an early stage, when they are more susceptible to treatment. The practice is credited with reducing death rates of some cancers by as much as 70 percent. Here’s what can happen when a person with no symptoms takes a screening test:

Small cancer: A small cancer is found that responds well to early therapy. The patient has the best chance for a full recovery and may even require less treatment.

False positive: A test can erroneously signal cancer in a healthy patient. Such false positives lead to additional tests that can be invasive, expensive and cause undue anxiety.

False negative: A test can miss a cancer that is present. Such false negatives can give patients a false sense of security that they have a clean bill of health.

Aggressive cancer: A test can detect an aggressive cancer whose outcomes aren’t improved by early detection.

Slow-growing cancer: A test can find small cancers that are slow-growing and might even go away on their own. The patient could be subjected to aggressive and invasive treatment, even though the tumor – if undetected – wouldn’t have posed a health threat.

Los Angeles Times

It seemed like a good idea at the time.

In 1984, Japan began screening the urine of 6-month-old infants for neuroblastoma, the most common type of solid tumor in young children. The test was simple and could show signs of cancer long before clinical symptoms arose.

Hundreds of infants went through the ordeal of diagnosis and treatment, but it didn’t reduce the number of tumors found later, including deadly ones. Almost none of the tumors caught by screening turned out to be dangerous – and more of the screened children died of complications from surgery and chemotherapy than from the cancer itself.

In 2004, health officials ended the program.

The United States is grappling with the same type of problem today. After decades of focus on the upside of cancer screening, public health experts are re-evaluating the wisdom of administering routine cancer screening tests to millions of asymptomatic people.

Although screening certainly saves lives, recent studies make it clear that it also leads to biopsies, surgeries, chemo and radiation – even some deaths – that otherwise would not have occurred.

That screening has a downside is not easy to accept, as evidenced by the furor over last week’s recommendation from the U.S. Preventive Services Task Force that most women wait until 50 to start routine mammograms, and then get them only every other year.

Although the decision was based on new scientific evidence that many more women are harmed than helped by annual tests starting at 40, it swiftly was attacked by physicians and policymakers who said they would ignore it.

The message that we’re over-screening for cancer isn’t necessarily a welcome one to the American public either.

A whopping 87 percent of U.S. adults believe that routine screening is “almost always a good idea,” and 74 percent believe early detection saves lives “most or all of the time,” according to a 2004 survey in the Journal of the American Medical Association. Most said they’d continue to get their screening tests even if their doctors advised against it.

Indeed, in the days following release of the task force’s recommendations, irate breast cancer survivors lighted up message boards to vent their anger at the notion that their lives were not worth saving.

Part of the outcry stems from the fact that so many people know someone who was diagnosed with breast cancer in her 40s and appeared to respond to early treatment. It’s natural to think of those women as the ones who would be hurt by a reduction in screening, psychologists say.

We’re not as well equipped to weigh the risks and benefits of the population at large.

“We think, ‘I’m sure glad my sister or my best friend got that done,’ ” said Julie Downs, director of the Center for Risk Perception and Communication at Carnegie Mellon University in Pittsburgh.

Also complicating matters is that it’s easy to identify cancer survivors whose tumors were caught by screening, but it’s nearly impossible to put a face on the individual who is hurt by over-screening.

Patients are also reluctant to give up on the idea that they can control their medical destiny through proactive measures, said Nancy Berlinger, a health care bioethicist at the Hastings Center, a research institute in Garrison, N.Y.

“Anything that suggests that early detection might not save lives is going to be deeply disturbing,” she said. “It suggests that we can’t do much to help ourselves.”

The public’s attachment to screening also reflects its faith in high-tech medicine, said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society in Atlanta.

“They want to believe that the new technology is the better technology,” he said. “Sometimes it is – sometimes it isn’t.”

The notion of catching cancers early so they would be easier to treat has been around since at least the 1930s, when doctors began advising women to conduct breast self-exams.

“That philosophy sounded right, so screenings were implemented,” said Dr. Therese Bevers, medical director of the Cancer Prevention Center at the University of Texas M.D. Anderson Cancer Center in Houston.

And in many cases, that strategy works. The American Cancer Society credits widespread use of mammograms for a 2 percent annual decrease in breast cancer deaths since 1990. Pap smears have slashed deaths from cervical cancer by more than 70 percent since they were introduced in the 1940s.

But finding cancers that respond to early treatment is only one of the potential outcomes from a screening test. Many tests produce false positives, prompting additional tests that can be invasive, expensive, time-consuming and anxiety-inducing.

A study published this spring in Annals of Family Medicine found that 60 percent of men and 49 percent of women had gotten at least one false positive result during three years of routine screenings for ovarian, prostate, lung and colorectal cancer. As a result, 22 percent of those women and 29 percent of those men had an invasive diagnostic procedure, the study found.

Other screening tests produce false negatives, giving patients and their doctors the incorrect impression that they have nothing to worry about.

Some tests detect aggressive cancers whose outcomes aren’t improved by early detection.

And some identify small cancers that grow so slowly they’d never compromise a patient’s health. Many would even resolve on their own.

Statisticians and epidemiologists know this. The problem is that there’s no way to tell which tumors are dangerous and need to be treated and which are harmless and would be best left alone. So all of them get treated, often aggressively. The medical establishment calls this overdiagnosis.

“Overdiagnosis is the hardest thing to explain to people,” said Dr. Stephen Taplin, chief of applied cancer screening research at the National Cancer Institute in Washington, D.C. “No individual woman can know if they’re overdiagnosed. They know they have cancer, and they’re scared to death. It’s completely justified.

“But if you look at people overall,” he added, “there are some people who suffered that scare unnecessarily. If they had never known about that cancer, it wouldn’t have affected their life.”

Such nuances weren’t considered when screening tests were implemented. Many were introduced before their effectiveness had been established through clinical trials. At the time, doctors didn’t see the need. But experience has prompted them to reconsider.

Some guidelines, including those for cervical cancer, have been amended to reflect a better understanding of cancer biology. The American College of Obstetricians and Gynecologists last week advised that most women get Pap tests less frequently because it’s known now that cervical cancer progresses slowly, and abnormal cells often resolve on their own, especially in younger women.

Despite outcry from patients who equate reduced screening with reduced care, it makes no sense to ignore scientific data that happen to be unpalatable, said Dr. George Sawaya, a researcher at the University of California, San Francisco, whose studies helped prompt the change in Pap test guidelines.

“It would be much more of a travesty if we didn’t change our guidelines in response to new information,” he said.

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