Mammograms Reduce Breast Cancer Mortality Risk By Half: Study

12/06/2011 01:24pm ET

Regular mammography screening may reduce women's risk of dying from breast cancer by half, according to a new study from the Netherlands. The decrease was even more pronounced among women ages 70 to 75.

"Our study adds further evidence that mammography screening unambiguously reduces breast cancer mortality," Suzie Otto, a senior researcher at the Erasmus medical center's department of public health in Rotterdam, said in a statement.

The new research, published Tuesday in the journal Cancer Epidemiology Biomarkers and Prevention, looked at 755 cases of women who died from breast cancer between 1995 and 2003 and more than 3,700 matched controls. The Netherlands has a nationwide screening program that invites women in the targeted age range -- between 50 and 75 -- to be screened by a mobile unit every two years. Estimates suggest that 80 percent of invitees participate in the program.

The new study documented a 49 percent reduction in breast cancer mortality among women who received at least three mammograms and a 84 percent reduction among women ages 70 to 75. In 1998, the Netherlands extended the upper age limit of testing to 75, making it the only public program screening women up to that age, the study's authors write.

"This is the first [study] to see those reductions in that older age range," co-author Dr. Harry J. de Koning, also of the Erasmus MC, told The Huffington Post. He called the Dutch research the largest case-control study to date to look at the effectiveness of mammography screening in practice.

De Koning suggested several possibilities for why the new research found such a pronounced impact on older women. The cancer growth rate at that age may be slower, making screening more effective, he said. Also, detecting cancer among those women might be easier. According to the U.S. National Cancer Institute, breast cancer tissue becomes less dense as women grow older. Mammograms of dense breasts can be more difficult to interpret.

In the U.S., the impact of and guidelines for mammography screening have been a source of debate. In 2009, the U.S. Preventive Services Task Force changed its recommendations, announcing that women should begin getting mammograms at age 50, not 40 as it had previously recommended, and every two years, not annually. The report with the revised recommendations said mammography screening reduced the breast cancer mortality rate by 15 percent and cited the potential for false positives in both film and digital mammography as possible harms.

However, influential groups including the American Cancer Society still recommend yearly mammograms starting at age 40.

De Koning acknowledged the ongoing discussion. Although the current study is specific to the Netherlands, which has a robust national program with "relatively high-quality standards," he said it could still have broader implications.

"In principle, if you do high-quality mammography screening, it's very applicable to all countries," he said. "We are, of course, happy to continue the debate, but this is one of the important studies that you can show women who really want to know all of the benefits and harms."