Canadian study raises questions about mammogram safety again, at least two local MDs are skeptical

CINCINNATI - Longstanding concerns about the safety and effectiveness of mammography spiked last month when The New York Times reported on a Canadian study of 90,000 women over 25 years that suggested the test for breast cancer could do more harm than good.

Local experts say the study is flawed in design and execution and runs counter to other research that shows the benefits of mammography.

“There’s been so many other rigorous studies, properly controlled and randomized, that have come out in the last couple of decades and have supported the importance of mammography in reducing mortality, or deaths, from breast cancer up to 30 percent,” saID Dr. Richard Budde, medical director of the Women’s Imaging Center at The Christ Hospital. “That data have been overwhelming in that regard.”

“Mammograms aren’t perfect,” saID Dr. Amy Argus, the director of UC Health’s Breast Imaging and Mammography. “But we find about 80 percent of breast cancers with mammograms.”

The Canadian study was published in The British Medical Journal on Feb. 11. In its  lengthy article, The New York Times called the study “one of the few rigorous evaluations of mammograms conducted in the modern era of more effective breast-cancer treatments.”

Best weapon or more harm than good?

From 1980 to 1988, the researchers randomly assigned more than 90,000 Canadian women to have regular mammograms and breast examinations by trained nurses, or to have breast exams alone. The study followed the women over 25 years.

The Times reported that the study found “the death rates from breast cancer and from all causes were the same in women who got mammograms and those who did not. And the screening had harms: One in five cancers found with mammography and treated was not a threat to the woman’s health and did not need treatment such as chemotherapy, surgery or radiation.”

Mammography is an X-ray examination that requires compressing breast tissue between a clear plate and a detector to capture an image from the nipple to the chest wall. The American Cancer Society recommends that a woman should get an annual mammogram starting at age 40.

Many studies in the United States and other countries have shown that mammography is the best weapon against breast cancer because it can see tumors that are often too small to feel in a breast exam. Breast cancer advocacy organizations such as the Susan G. Komen Foundation were instrumental in pushing for insurance coverage of mammograms.

In the days after the Canadian study was published, the Komen Foundation issued a cautionary statement :

“This study adds to a growing body of evidence that mammography is an imperfect screening tool for breast cancer. We agree. It is based on 1950s technology and can lead in some cases to over diagnosis and over treatment of breast cancer.”

Study tools, methods "troubling"

Argus and Budde, the local specialists, say they are puzzled at the attention that the Canadian study is receiving now.

They point out that the study published last month was merely an update of research first released in 2005. At that time, the doctors said, the problems with the study were obvious and disqualifying, among them:

  • Researchers used outdated equipment
  • Personnel performing the mammograms and breast exams were not well-qualified
  • Followup with study subjects was limited to phone calls

The study “was pretty much discredited for its poor design, and the technology used was poor,” Argus said. “The mammograms they used back then were nothing of the quality that we have now. And the machines they used were below state-of-the-art even for 1980.”

Just as troubling, Budde said, was how the study subjects were selected. Before any of the 90,000 women had mammograms through the study, they received breast exams, and anyone with a mass that could be felt was given a mammogram. Everyone else received only breast exams through the study.

“That generally violates the standard research protocol, to take someone who has a known problem, who is symptomatic, and throwing her into the screening arm (of the study),” Budde said. “That just doesn’t make sense for a truly randomized study.”

Studies aside, it comes down to the patient

Argus and Budde also question the study’s conclusion that mammograms could do more harm than good by exposing women to needless X-ray radiation and generating an over diagnosis of breast cancer by as much as 22 percent. Argus said a recent Harvard study indicated that of all its patients over the past 10 years, 70 percent of cancer deaths came from the 20 percent of patients who were not screened.

“No way is that all over diagnosis.”

Budde said most studies conducted on mammography put the over diagnosis rate at about 10 percent.

“So the question is: Why is theirs so much different?” Breast cancer in general grows slowly, she said, and a mammogram image only reveals so much about its lethality.

“How are you going to know? Once we see a suspicious lesion, and we suggest biopsy, we want to know what it is right then

and there, in that snapshot in time, and get the best idea in terms of tumor markers. We want to know how aggressive the lesion is and how to plan the proper therapy,”Budde said. “We’re not going to know unless we biopsy. You can’t predict that just from the imaging alone. And so that’s the major dilemma.”

In the end, Argus and Budde said, there is no substitution for a woman looking at all her options.

“It comes down to the patient talking to her doctor and understand her overall risk level,” Budde said. “We want the patient to make a well-educated decision. I firmly believe that sound scientific data clearly support annual screening beginning at age 40. But ultimately, it comes down to the patient herself.”

Connect with WCPO contributor Anne Saker on Twitter: @apsaker .

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