Mammograms don't save as many lives as women think

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A doctor exams mammograms a clinic in Nice, south eastern France January 4, 2008.

Credit: Reuters/Eric Gaillard

By Julie Steenhuysen

CHICAGO | Tue Oct 25, 2011 3:02pm EDT

CHICAGO (Reuters) - Many women who have survived breast cancer often say it was a mammogram that "saved their life," a powerful testimonial that can encourage other women to get regular breast cancer screening tests.

But what are the chances that the test actually saved a woman's life? Not that great, according to a new analysis published in the Archives of Internal Medicine on Monday.

"The numbers suggest that at most, 13 percent of those diagnosed with breast cancer have been helped. That means the other 87 percent have not been helped," Dr. Gilbert Welch of Dartmouth College, who led the study, said in a telephone interview.

"That is important when we keep hearing these stories from breast cancer survivors," he said.

Welch said women who tell their stories about surviving breast cancer can be a powerful inducement for other women to get tested for breast cancer, and as mammogram technology has improved, the chances are even greater that doctors will find something suspicious.

But early detection for some women may not be much of a benefit, especially if a cancer is slow growing, Welch and colleagues say. And many women may be diagnosed and treated for a cancer growing so slowly it might never have caused any symptoms or threatened their lives.

The findings add new fodder to the simmering debate over the benefits of screening healthy people for cancer. Earlier this month, the government-backed U.S. Preventive Services Task Force recommended that healthy men not get a common blood test for prostate cancer, causing an uproar among cancer specialists who fear more men will die from prostate cancer.

In 2009, the same group recommended that women under 50 not get routine mammograms. For women 50 and older, it recommended the test only every other year, rather than yearly, causing an outcry from breast cancer advocacy groups.

But screening tests have both benefits and risks, says Welch, who views the current debate as positive for patients who are starting to think more about the risks of screening.

An earlier study by Welch found that routine screening for prostate cancer has resulted in as many as 1 million American men being diagnosed with tumors who might otherwise have suffered no ill effects from them.

In the latest study, Welch and colleagues looked to see how much mammography reduces deaths from breast cancer.

They found that for 50-year-old women whose breast cancers were diagnosed by a mammogram, there was a 13 percent chance that the screening test saved her life.

The question, then, becomes how to preserve the benefit of mammogram without exposing so many women to the harms of overdiagnosis -- which include being treated for cancers that might not cause harm, Welch said.

He said breast cancer screening technology has become better and better at spotting tiny cancers on the assumption that the earlier a cancer is detected, the better the chances of cancer survival.

But Welch said as treatments for breast cancer get better, the need for very early diagnosis is less great.

"For years we've been looking harder and harder for cancer. I think the time has come to ask the question, 'What if we looked a little less hard?'"

Dr. Timothy Wilt of the Minneapolis Veterans Administration, who wrote a commentary on the findings in the same journal, said the study gives doctors science-based information to share with patients, who are often influenced by anecdotes.

"Because survivor stories are often so powerful, but inaccurate, they can result in people making healthcare decisions that are not science based and may be wrong," he said.

(Editing by Cynthia Osterman)

(This story was corrected in paragraph 8 to show mammogram recommendations refer to women under the age of 50, not 40)

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Mammograms Only Occasionally Save Lives, Analysis Finds

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Some doctors and public-health experts have stirred controversy in recent years by arguing that aggressive breast-cancer screening does more harm than good. Many health professionals disagree, but perhaps the most compelling critics of the less-is-more philosophy are the many breast cancer survivors who claim that a routine mammogram saved their lives.

These survivor anecdotes — which often turn up in the media — may be causing the public to overestimate the true value of mammograms, a new study suggests. In an analysis published this week in the Archives of Internal Medicine, researchers at Dartmouth estimate that only about 1 in 8 women whose breast cancer was identified during a routine mammogram actually owe their lives to the screening.

This estimate doesn't mean that women shouldn't bother to get mammograms, but it does suggest that overly frequent screening can result in overtreatment, the authors say. Many tumors identified during routine mammograms would have grown very slowly (if at all) and would never have threatened a woman's life, says Dr. H. Gilbert Welch, one of the coauthors of the analysis.

"A certain fraction of women are being treated for a disease that was never going to bother them," says Dr. Welch, a professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice, in Hanover, N.H.

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The U.S. Preventive Services Task Force (USPSTF), a government advisory panel that issues guidelines on cancer screening, recommends that women start having mammograms every other year when they turn 50, while women who have risk factors for breast cancer should talk with their doctor about starting screening earlier. (Prior to 2009, the panel recommended annual mammograms for all women beginning at age 40.) A large study published last week found that biennial screening resulted in fewer false alarms and unnecessary biopsies than annual screening.

The results of the new analysis should reassure women with average breast-cancer risk that it's safe to wait until age 50 — or later — to begin mammograms, Dr. Welch says. However, he adds, women who would prefer to undergo screening earlier or more frequently should do so if it will make them more comfortable. "It's generally a really close call, and how patients feel really matters," he says.

To investigate the value of mammography in terms of lives saved, Dr. Welch and his colleague, Brittney Frankel, used breast-cancer data from the National Cancer Institute and the Centers for Disease Control and Prevention to calculate a woman's likelihood of developing breast cancer over a 10-year period, the likelihood that the cancer would have been detected by mammography, and a woman's risk of dying from breast cancer over a 20-year period.

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Using the relevant data for a hypothetical 50-year-old woman who received a breast cancer diagnosis following a routine mammogram, the researchers estimate that the probability that the mammogram will be responsible for saving her life is about 13%. And even that estimate may be high, they say: mammograms prevent fewer deaths today than they did 20 or 30 years ago (thanks to better treatment that has made early detection less crucial), so the actual probability could be as low as 3%.

"Women need to understand their trade-offs here," Dr. Welch says. "The reason to be screened isn't because you've heard a lot of survivor stories. Some of those women have not benefited [from screening]."

Dr. Timothy Wilt, a researcher at the Minneapolis Veterans Affairs Center who specializes in chronic disease outcomes, says that breast-cancer diagnosis and treatment can even be harmful in some cases. Radiation treatment, for instance, can cause disfigurement, accelerate blockage of arteries in the heart, and increase the risk of secondary cancers, he says.

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"Looking harder and treating more doesn't always help people live longer and live better," says Dr. Wilt, who coauthored an editorial accompanying the study and is a member of the USPSTF. The push toward less screening "is not about rationing care," he adds. "It's about making good health care decisions to help patients live better and live longer."

Dr. Laura Esserman, the director of the breast care center at the University of California, San Francisco, says that doctors and women should shift their focus away from breast-cancer screening and toward prevention. For instance, Esserman says, women can reduce their risk of breast cancer by maintaining a healthy weight, exercising regularly, and minimizing their alcohol consumption.

"Mammography has some value," she says, "but I think it's pretty clear that the public has overvalued it and a lot of people who push it have overvalued it."

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Risk of annual mammograms

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Women with annual mammograms are more likely to experience anxiety from false-positive results. The probability of having an unnecessary biopsy is higher with annual screeningFalse-positive results are a source of anxiety and common in many mammogramsAnnual mammograms not conclusively more effective than biennial screeningsFederal advisory group recommendeds most women get screened once every two years

(Health.com) -- Women who have a screening mammogram every other year are substantially less likely than those who opt for annual screening to experience false-positive results and biopsies that turn out to be unnecessary, according to a new study funded by the National Cancer Institute.

Using data from a nationwide network of breast-cancer registries, researchers analyzed more than 386,000 mammograms from about 170,000 women who began having the breast X-rays between 1994 and 2006.

Over 10 years of screening, the study estimates, 61% of women who have annual mammograms and 42% of women who have biennial mammograms will be called back at least once for a follow-up test that reveals they do not in fact have cancer.

The probability of having an unnecessary biopsy is similarly higher with annual screening. Depending on the age at which they begin screening, 7% to 9% of women who have annual mammograms and 5% to 6% of those who have biennial mammograms will have unnecessary biopsies over a 10-year period, according to the study, which appears this week in the Annals of Internal Medicine.

Health.com: 25 breast cancer myths busted

Annual mammograms were not conclusively more effective than biennial screening at identifying dangerous late-stage cancers, although a slightly higher percentage of women in the biennial group did develop these cancers.

The researchers caution, however, that the small number of women in the study who received a diagnosis of invasive breast cancer (4,492) prevents them from drawing firm conclusions about the effectiveness of one screening schedule over another. A larger study will be needed to clarify that point, they say.

The findings don't show that biennial screening is better than annual screening, or vice versa, but rather that false positives -- a source of anxiety for many women -- are common and "part of the process of screening mammography," says lead researcher Rebecca Hubbard, Ph.D., an assistant investigator at the Group Health Research Institute, the research arm of a nonprofit health plan in Seattle.

"I don't think there is any one right answer," Hubbard says. "I think it's a personal decision where every single woman has to think about what is her risk tolerance, how would she handle a false positive, and her own personal breast cancer risk."

Health.com: How to cut your breast cancer risk at any age

Doctors and researchers have been debating the pros and cons of annual mammograms for years, but the question has taken on added urgency since 2009, when a federal advisory group recommended that most women have mammograms every other year beginning at age 50, rather than every year beginning at age 40.

The group, known as the United States Preventive Services Task Force, suggested that screening decisions should be based on a woman's individual risk as well as her "values" regarding the potential benefits and harms of more frequent screening.

Laura Esserman, M.D., the director of the breast care center at the University of California, San Francisco, says the new study validates the task force's recommendation and "confirms that biennial screening is the best way to go." (Esserman was involved in neither the task force nor the study.)

The increased risk of advanced cancer associated with biennial as opposed to annual screening is "so tiny that [it's] not even relevant," Esserman says. Mammography is primarily useful for catching slow-growing cancers, she says, while fast-growing cancers -- which are more common among younger women, and tend to cause a palpable mass in the breast -- grow so quickly that even annual mammograms could miss them.

Health.com: Fighting the cancer a mammogram can't catch

But Daniel B. Kopans, M.D., a professor of radiology at Harvard Medical School, in Boston, says the implications of the study are not so clear-cut. Studies like this one that analyze large amounts of registry data have certain inherent limitations, even when mitigating factors such as age and family history of cancer are taken into account, he says.

Unlike studies in which women are randomly assigned to receive either annual or biennial screening, the method used by Hubbard and her colleagues can't rule out the possibility that the women who chose to get annual mammograms are different from their peers in unidentified ways that may have skewed the findings, Kopans says.

"The reason that oncologists have not been calling for a cessation to annual screening beginning at the age of 40 is because they know well that the best way for their therapies to cure breast cancer is to find it early," Kopans says. "It is, probably, not a good idea to set the clock back by lengthening the screening interval."

Health.com: How to help a loved one cope with breast cancer

The study has some important shortcomings. For instance, relatively few of the women completed a full decade of annual or biennial mammograms, so the researchers had to resort to statistical modeling to estimate the 10-year probability of false positives and unnecessary biopsies. And most of the mammograms included in the study were traditional film-screen mammograms, not the digital mammograms now in widespread use.

It's not clear how the change in technology might affect the relevance of the findings. In another study in the same issue of the journal, Hubbard and her colleagues compared digital and film mammography. Both techniques were similarly effective, they found, although digital mammography was better at identifying tumors in extremely dense breast tissue and estrogen receptor negative tumors, both of which are more common among women in their 40s.

Hubbard stresses that the greater likelihood of false positives associated with more frequent mammograms shouldn't dissuade women from getting the tests altogether. "It's really important that women are getting screened, and that concern or anxiety about false positive results doesn't become a barrier for participating," she says.

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Risk of annual mammograms

AppId is over the quota
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Women with annual mammograms are more likely to experience anxiety from false-positive results. The probability of having an unnecessary biopsy is higher with annual screeningFalse-positive results are a source of anxiety and common in many mammogramsAnnual mammograms not conclusively more effective than biennial screeningsFederal advisory group recommendeds most women get screened once every two years

(Health.com) -- Women who have a screening mammogram every other year are substantially less likely than those who opt for annual screening to experience false-positive results and biopsies that turn out to be unnecessary, according to a new study funded by the National Cancer Institute.

Using data from a nationwide network of breast-cancer registries, researchers analyzed more than 386,000 mammograms from about 170,000 women who began having the breast X-rays between 1994 and 2006.

Over 10 years of screening, the study estimates, 61% of women who have annual mammograms and 42% of women who have biennial mammograms will be called back at least once for a follow-up test that reveals they do not in fact have cancer.

The probability of having an unnecessary biopsy is similarly higher with annual screening. Depending on the age at which they begin screening, 7% to 9% of women who have annual mammograms and 5% to 6% of those who have biennial mammograms will have unnecessary biopsies over a 10-year period, according to the study, which appears this week in the Annals of Internal Medicine.

Health.com: 25 breast cancer myths busted

Annual mammograms were not conclusively more effective than biennial screening at identifying dangerous late-stage cancers, although a slightly higher percentage of women in the biennial group did develop these cancers.

The researchers caution, however, that the small number of women in the study who received a diagnosis of invasive breast cancer (4,492) prevents them from drawing firm conclusions about the effectiveness of one screening schedule over another. A larger study will be needed to clarify that point, they say.

The findings don't show that biennial screening is better than annual screening, or vice versa, but rather that false positives -- a source of anxiety for many women -- are common and "part of the process of screening mammography," says lead researcher Rebecca Hubbard, Ph.D., an assistant investigator at the Group Health Research Institute, the research arm of a nonprofit health plan in Seattle.

"I don't think there is any one right answer," Hubbard says. "I think it's a personal decision where every single woman has to think about what is her risk tolerance, how would she handle a false positive, and her own personal breast cancer risk."

Health.com: How to cut your breast cancer risk at any age

Doctors and researchers have been debating the pros and cons of annual mammograms for years, but the question has taken on added urgency since 2009, when a federal advisory group recommended that most women have mammograms every other year beginning at age 50, rather than every year beginning at age 40.

The group, known as the United States Preventive Services Task Force, suggested that screening decisions should be based on a woman's individual risk as well as her "values" regarding the potential benefits and harms of more frequent screening.

Laura Esserman, M.D., the director of the breast care center at the University of California, San Francisco, says the new study validates the task force's recommendation and "confirms that biennial screening is the best way to go." (Esserman was involved in neither the task force nor the study.)

The increased risk of advanced cancer associated with biennial as opposed to annual screening is "so tiny that [it's] not even relevant," Esserman says. Mammography is primarily useful for catching slow-growing cancers, she says, while fast-growing cancers -- which are more common among younger women, and tend to cause a palpable mass in the breast -- grow so quickly that even annual mammograms could miss them.

Health.com: Fighting the cancer a mammogram can't catch

But Daniel B. Kopans, M.D., a professor of radiology at Harvard Medical School, in Boston, says the implications of the study are not so clear-cut. Studies like this one that analyze large amounts of registry data have certain inherent limitations, even when mitigating factors such as age and family history of cancer are taken into account, he says.

Unlike studies in which women are randomly assigned to receive either annual or biennial screening, the method used by Hubbard and her colleagues can't rule out the possibility that the women who chose to get annual mammograms are different from their peers in unidentified ways that may have skewed the findings, Kopans says.

"The reason that oncologists have not been calling for a cessation to annual screening beginning at the age of 40 is because they know well that the best way for their therapies to cure breast cancer is to find it early," Kopans says. "It is, probably, not a good idea to set the clock back by lengthening the screening interval."

Health.com: How to help a loved one cope with breast cancer

The study has some important shortcomings. For instance, relatively few of the women completed a full decade of annual or biennial mammograms, so the researchers had to resort to statistical modeling to estimate the 10-year probability of false positives and unnecessary biopsies. And most of the mammograms included in the study were traditional film-screen mammograms, not the digital mammograms now in widespread use.

It's not clear how the change in technology might affect the relevance of the findings. In another study in the same issue of the journal, Hubbard and her colleagues compared digital and film mammography. Both techniques were similarly effective, they found, although digital mammography was better at identifying tumors in extremely dense breast tissue and estrogen receptor negative tumors, both of which are more common among women in their 40s.

Hubbard stresses that the greater likelihood of false positives associated with more frequent mammograms shouldn't dissuade women from getting the tests altogether. "It's really important that women are getting screened, and that concern or anxiety about false positive results doesn't become a barrier for participating," she says.

Copyright Health Magazine 2010

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