New Studies Show the Downside Of Cancer Screening

Doctors say screening can harm, but others say it still brings benefits.

August 31, 2009, 5:32 PM

Sept. 1, 2009&#151; -- Recent years have seen a rise in encouragement for cancer screenings, but a number of studies have reminded physicians and their patients of the old saying about free lunches.

That is, nothing good comes without a cost.

Two studies released Monday -- one looking at prostate cancer and the other at breast cancer -- appearing in the Journal of the National Cancer Institute, show that increased screening brings false positives and the costs of emotional anguish and sometimes unnecessary treatment.

"The fact that it is a surprise to so many physicians and so many patients is a symptom of the debate taking place now regarding health care reform," said Dr. Thomas Schwenk, a family physician with the University of Michigan, commenting on the prostate cancer study. "The American approach to medical care is to always do more, irrespective of whether it has any value, and even in the face of data showing that doing more causes harm."

While the prostate cancer study, which utilized data from the National Cancer Institute (not affiliated with the journal that published the study), and the breast cancer study, which used data from women being screened in the province of Ontario, Canada, were in two different cancers in two different populations, both studies came to similar conclusions; in short, a lot of patients were receiving unnecessary treatments.

In the breast cancer screening study, women in Ontario were given a clinical breast exam in addition to mammography.

"I think that women should be informed of the benefits and limitations if they have a clinical breast exam in addition to mammography," said Anna Chiarelli, an epidemiologist at the University of Toronto and one of the authors of the breast screening study. "For every additional cancer found there were 55 false positives."

Meanwhile, according to the prostate cancer study's authors, between the years 1986 and 2005, 1 million "additional" men were diagnosed with prostate cancer.

"Given the considerable time that has passed since PSA screening began, most of this excess incidence must represent overdiagnosis," concluded Dr. H. Gilbert Welch, professor of medicine and community and family medicine at Dartmouth Medical School and Dr. Peter C. Albertsen, chief and program director of the division of urology at the University of Connecticut Health Center.

"It is of note that countries that do not have widespread screening as a policy have seen some declines in prostate mortality without the harm of frequent overdiagnosis," said Dr. Otis Brawley of the American Cancer Society in a related editorial.

Even If a Free Lunch Is Not Free, It's Still Lunch

While acknowledging the costs of false positives in cancer screenings, physicians said it is important not to look past the benefits those screenings bring as well.

"There is no question that prostate cancer is being over-detected and over-treated today," said Dr. Peter Scardino, chair of the department of surgery at Memorial Sloan-Kettering Cancer Center. "It is, however, a serious mistake to suggest that PSA cannot detect many potentially lethal cancers at a time when they can be cured with surgery and radiation. While there is some argument about the benefits of PSA screening, prostate cancer mortality rates have declined by 50 percent over the last 15 years."

Dr. Patrick Walsh, a professor of urology at Johns Hopkins, argued that the prostate study is deeply flawed.

"The problem with the article is simple," he said. "In 1986 there was an enormous reservoir of men in the population with advanced asymptomatic incurable prostate cancer -- so that when they were diagnosed with cancer, treatment had no effect on their outcome. Then, beginning in the mid- to late-1990s, we finally were seeing men who were curable and who were going to live long enough to be cured."

The study does not show, said Walsh, any benefit for the patients who were diagnosed at the end of the study period, since the 15 to 20 years it might take some patients to die (from a slow-growing tumor) has not yet passed.

The Benefits of Ongoing Training

Dr. Marisa Weiss, the founder of, had similar criticisms of the breast cancer study for not highlighting the benefits of clinical breast exams -- although she noted that part of the issue was the difference between the American and Canadian healthcare systems.

The Canadian study, she noted, may have only included one exam for most of the women involved, since it only lasted two years, she said, and the medical professional doing the exam may not have been the woman's regular doctor.

"When you're doing your first study and you know you're going to be examining that person once…you might be more likely to find something or check something out than if you had an ongoing relationship with that person and you knew you'd be seeing them again at a short interval," said Weiss.

That would contribute to a high rate of false positives, she said.

"Doctors and nurses could benefit by further training…but I do think the risk of false positives is decreased by regular repetition," said Weiss.

Like the study author, she thought the study showed that more emphasis should be placed on having a standardized breast exam. But she did not agree with another conclusion of the study.

"There's a lot at risk because 20 percent of breast cancers are detected by the women or doctor, not detected mammographically," said Weiss. "I'm very worried about a result that would give up the opportunity for women to find breast cancers earlier than they would be detected by mammogram alone."

Better Applications

In his editorial, Brawley noted that part of the problem with the emphasis on screening is that it has drawn funding from other areas.

"Indeed, over the past 20 years, many research dollars were spent addressing the question 'how can men be encouraged to get screened?' when projects to better understand prostate cancer biology were not funded," he said.

Several doctors noted that given the wide variety of diseases that make up any one form of cancer, more research was needed to determine the best way to tackle a growth in a particular patient.

"Like any screening test, the results have to be interpreted," said Dr. Scott Fields, a family practitioner with Oregon Health and Sciences University. "In this case, it is very problematic because prostate cancer often is present but causing no problems. And we really have little way of differentiating people who will be affected."

Effects of False Positives

In a twist, it appears that while studies may have focused on finding ways to increase screenings, many more are looking at the possible impacts of false positives.

One such study, appearing in the Annals of Family Medicine earlier this year and looking at prostate, colorectal, lung and ovarian cancers found that repeated screenings for cancers recommended by current protocols yield a number of false positives. After 14 tests, the chance of getting a false positive rose to over 60 percent of all men and nearly 49 percent of all women.

"I think the bottom line message is that traditionally, when people have gotten public health messages about screening, it's been oversimplified and presented in a positive light only," said Dr. Jennifer Miller Croswell, of the Office of Medical Applications of Research at the National Institutes of Health, one of the study's lead authors. "What we forget sometimes…is that these are medical interventions and they do have the potential for benefits and harms."

In a time when the costs of various treatments are put under the microscope during debate on health care reform, cancer screening presents an uncomfortable challenge, because setting a level of screening invariably leads to an acceptance that certain cases will be missed – thereby putting a dollar value on the lives lost.

"The problem with a false positive is that it can trigger this repeated long-term follow-up, and all these things add cost," said Croswell.

Ultimately, deciding how many false negatives to accept leaves the realm of medicine. "That's honestly a policy decision that can be made," said Croswell.

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