Yearly mammograms in middle-age women do not reduce breast cancer deaths – these tests are essentially as good as physical examination alone, according to a new 25-year study from Canada.

The study, which included nearly 90,000 women ages 40 to 59, is the latest to question the value of routine mammography. The researchers found the same number of women died of breast cancer over 25 years, regardless of whether they underwent yearly mammograms or not.

Mammography is performed routinely to screen women for breast cancer, with the goal of early diagnosis. But it is highly debated whether this screening saves lives. In some cases, early detection does not necessarily mean the cancer can be cured, and in some others, treatments work even if cancer is discovered at later stages. [6 Foods That May Affect Breast Cancer Risk]

It is also controversial whether the potential benefits of mammograms outweigh the harm done by overdiagnosis and overtreatment. The new study found that about 22 percent of breast cancers detected by mammograms were what researchers call over-diagnosed, meaning the mammograms revealed tumors that didn’t cause disease symptoms, and would not have reduced a woman’s life span if left undetected.

The new findings suggest that “the rationale for […]