Canadian study revives debate about mammograms

2/13/2014

By MARILYNN MARCHIONE

By MARILYNN MARCHIONE

AP Chief Medical Writer

A Canadian study that many experts say has major flaws has revived debate about the value of mammograms. The research suggests that screening X-rays don't lower the risk of dying of breast cancer, while finding many tumors that don't need treatment.

The study gives longer follow-up on nearly 90,000 women who had annual breast exams by a nurse to check for lumps plus a mammogram, or the nurse's breast exam alone. After more than two decades, breast cancer death rates were similar in the two groups, suggesting little benefit from mammograms.

The study didn't compare mammograms to no screening at all, as most other research on this topic has. Many groups have not endorsed breast exams for screening because of limited evidence that they save lives.

Critics of the Canadian study also say it used outdated equipment and poor methods that made mammograms look unfairly ineffective.

The study was published Wednesday in British journal BMJ.

Breast cancer is the leading type of cancer and cause of cancer deaths in women worldwide. Nearly 1.4 million new cases are diagnosed annually. Many studies have found that mammograms save lives, but how many and for what age groups is debatable. It also causes many false alarms and overtreatment of cancers that wouldn't have become life-threatening.

In the U.S., a government-appointed task force for screening advice doesn't back mammograms until age 50, and then only every other year. The American Cancer Society recommends them every year starting at age 40. Other countries screen less aggressively. In Britain, for example, mammograms are offered every three years.

The Canadian study initially reported that after five years of screening, 666 cancers were found among women given mammograms plus breast exams versus 524 cancers among those given the exams alone.

After 25 years of follow-up, about 500 in each group died, suggesting mammograms weren't saving lives. The similarity in death rates suggests that the 142 cancers caught by mammograms represent overdiagnosis — tumors not destined to prove fatal, study leaders concluded.

The work was immediately criticized. The American College of Radiology and Society of Breast Imaging called it "an incredibly misleading analysis based on the deeply flawed and widely discredited" study. Mammograms typically find far more cancers than this study, suggesting the quality was poor, the groups contend.

In a letter posted by the medical journal, Dr. Daniel Kopans, a radiologist at Harvard Medical School, described outdated machines and methods he saw in 1990, when he was asked to review the quality of mammograms used in the study.

"I can personally attest to the fact that the quality was poor," he wrote. "To save money they used secondhand mammography machines" that gave poor images, failed to properly position breasts for imaging, and did not train radiologists on how to interpret the scans, he wrote.

The study leader, Dr. Anthony Miller of the University of Toronto, said it was "completely untrue" that inferior equipment or methods were used.

Still, the study highlights the fact that mammograms are an imperfect tool that lead to many false alarms, needless biopsies and treatment of many tumors that would never threaten a woman's life.

"Overdiagnosis is not an anomaly in the study from Canada. This has been compellingly demonstrated in research from the U.S. and Europe," said another study leader, Dr. Cornelia Baines of the University of Toronto.

Dr. H. Gilbert Welch, a professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice in New Hampshire, spoke on the issue at the San Antonio Breast Cancer Symposium in December.

"Screening is a choice, not a public health imperative. There are trade-offs here," he said.

"The people who stand to gain the most from screening are the people at greatest risk of the disease" — older women who are more likely to have breast cancer and those not too old that they are likely to die of something else, he said.

Death rates from breast cancer have fallen mostly because of dramatic improvement in treatments, he and other doctors have said.

"The better we are at treating clinically evident disease, the less important it becomes to find it early," Welch said.

A big caveat: The Canadian study was on routine mammograms to screen healthy women. No one doubts the value of diagnostic mammograms — more detailed X-rays when a problem is suspected or after a lump has been found.

------

AP Medical Writer Maria Cheng contributed to this report from London.

------

Marilynn Marchione can be followed at http://twitter.com/MMarchioneAP

comments powered by Disqus
I commented on a story, but my comments aren't showing up. Why?
We provide a community forum for readers to exchange ideas and opinions on the news of the day.
Passionate views, pointed criticism and critical thinking are welcome. We expect civil dialogue.
Name-calling, crude language and personal abuse are not welcome.
Moderators will monitor comments with an eye toward maintaining a high level of civility in this forum.

If you don't see your comment, perhaps you ...
... called someone an idiot, a racist, a moron, etc. Name-calling or profanity (to include veiled profanity) will not be tolerated.
... rambled, failed to stay on topic or exhibited troll-like behavior intended to hijack the discussion at hand.
... included an e-mail address or phone number, pretended to be someone you aren't or offered a comment that makes no sense.
... accused someone of a crime or assigned guilt or punishment to someone suspected of a crime.
... made a comment in really poor taste.

MULTIMEDIA