Mammograms Do Not Help Reduce Breast Cancer Deaths: Study

A 25-year study reveals that yearly mammograms do not prevent breast cancer deaths and are not necessarily better than simple breast examinations.

A researcher from the University of Toronto began the study in 1980 to compare breast cancer incidence and mortality rates in 89,835 Canadian women aged between 40 and 59. The participants were divided in two groups: women who received five annual screening and women who did not receive any test. Women of ages 40 to 49 in the mammography group, and all women aged 50 to 59 in both groups also received annual physical breast examinations.

In the five year screening period, 666 invasive breast cancers were diagnosed in the mammography arm group and 524 in the controls. Out of these 180 women in the mammography arm and 171 women in the control arm died of breast cancer during the 25 year follow-up period.

 During the entire study period (25 years), nearly 3250 women from the mammography arm and 3133 women from the control were diagnosed with breast cancer. The total number of deaths from both groups was approximately 500 each.

According to the report, "The cumulative mortality from breast cancer was similar between women in the mammography arm and in the control arm."

The researchers found that annual mammography doe not reduce death rates due to breast cancer in the susceptible groups. It was additionally discovered that nearly 22 percent of women were over-diagnosed.

The finding raises questions about the credibility of the tests in checking mortality in breast cancer affected patients. Overdiagnosis means that a cancer detected during screening might not necessarily manifest during the lifetime of that person.

The overselling of mammography has led to the "popularity paradox," said first author Dr. Anthony Miller, professor emeritus in the Dalla Lana School of Public Health at the University of Toronto in an interview to The Windsor Star. "The more cancers found as a result of screening, and the more people who believe, wrongly, that screening has saved their lives, the more the number of cancer "survivors" and advocates for screening grows."

"It is increasingly being recognized that there are significant harms from screening and that screening can do much less now than 40 years ago because of improved therapy," Cornelia Baines co-author of the study said in an email reply to the Windsor Star.

The results are not expected to bring in any new guidelines for breast cancer screening. Richard. C. Wender, the chief of cancer control for the American Cancer Society, said the society and its panel of experts will review the studies on mammography. He also added that data from the previous trials of mammography have shown reduction in death rates by at least 15 -20 percent, reports New York Times.

The American Cancer society recommends clinical breast exams once every three years for women aged above 20 and mammogram screenings for those above 40. In the U.S., nearly 37 million mammograms are performed per year and each screening costs approximately $100, according to the NY Times.