Study Finds Mammograms Are Not Reducing Mortality Rates



Yearly mammograms will not reduce the rate of breast cancer mortality, a new study states. Published Tuesday in the British Medical Journalit reports the findings of a study that began tracking two groups, a total of 89,835 women, in 1980. For one group, mammograms and physical examinations occurred on an annual basis. In the control group, there was no annual mammography, but physical examinations did take place, and the participants remained under the care of their family doctor. Both groups were then followed for a period of 25 years.

The purpose of the study was to assess the effectiveness of mammography in reducing breast cancer mortality. Regular mammogram screening takes place with this goal in mind, and to assess whether or not it is a worthwhile process, the researchers state it “must be evaluated in randomised screening trials, with breast cancer mortality as the endpoint.”

For five years (between 1980 and 1985) screening took place. During that time, 666 invasive cancers were diagnosed in the mammography group, and 524 in the control sector. In the former, 180 women died, and 171 died from the latter. After studying the findings the researchers found that, “Annual mammography does not result in a reduction in breast cancer specific mortality for women aged 40-59 beyond that of physical examination alone or usual care in the community.”

Furthermore, regular mammograms could be leading to “over-diagnosis.” When the researchers evaluated the cases that were detected, 106 of invasive cancers (or, 22 percent) were determined to be over-diagnosed. For every 424 women who received mammography screening in the trial, one was over-diagnosed. This means that what was found would not necessarily have become become clinically apparent during the woman’s life.

A general campaign in Canada recruited women to the study. In order to be eligible, they needed to be between 40 and 59 years old. Participants could not have had a mammogram in the preceding twelve months. Women who had a history of breast cancer and women who were pregnant were barred from participation. After a clinical examination, and being taught by a nurse how to conduct a self-examination, the women were randomly split into the two groups. 

The research team reached the conclusion that, “In technically advanced countries, our results support the views of some commentators that the rationale for screening by mammography should be urgently reassessed by policy makers.” However, this finding cannot be generalized globally. The study adds that women need to have access to the best clinical care, education, and early detection methods in order to diagnosis as many cases as possible while tumors are still under 2 cm in size.

“As time goes by, we do indeed need more efficient mechanisms to reconsider priorities and recommendations for mammography screening and other medical interventions,” an editorial published to accompany the study states. “This is not an easy task, because governments, research funders, scientists, and medical practitioners may have vested interests in continuing activities that are well established.”

The Susan G. Komen organization responded to the study on Tuesday. “This study adds to a growing body of evidence that mammography is an imperfect screening tool for breast cancer. We agree,” a blog post states. “It is based on 1950s technology, and can lead in some cases to over-diagnosis and over-treatment of breast cancers. The problems with mammography have been established for many years.” Instead, the organization wants research to be devoted to better methods for early detection.

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