When the U.S. Preventive Services Task Force (USPSTF) changed its screening-mammography guidelines last year — recommending against routine annual mammograms for women in their 40s — the announcement met with some resistance. Now a new study from Norway supports the USPSTF’s decision. Based on an extensive review of the existing data, the USPSTF recommended that women delay routine screening mammograms until age 50. According to the data, the panel said, for women under 50 the risks of routine mammograms — including false-positive results, anxiety, and unnecessary and invasive treatments — outweighed the potential benefit in mortality reduction. (More on Time.com: Clinical Trial Dilemma: Save Lives Now — or Later?)
The new Norwegian study, published Thursday in the New England Journal of Medicine, tends to support that conclusion. The study found a small reduction in breast-cancer mortality in women aged 50 to 69 who were getting routine screening mammograms, compared with women who were not. But the findings suggest that most of that small benefit was due to factors other than mammography. The Washington Post reports:
Regular mammograms reduced the risk of dying from breast cancer by just 10%, which is far lower than had been thought, even by the panel [the USPSTF] that raised questions about mammograms during the health debate.
The overall breast cancer death rate in the United States has been decreasing two percent a year since 1990. Previous estimates had attributed 15 to 23 percent of the reduction in breast cancer mortality to mammograms. Instead, the findings indicate that the drop in deaths from breast cancer have come mostly as a result of other factors, such as better treatment and awareness of the disease.
The researchers studied data from more than 40,000 breast-cancer patients, analyzing the mortality rates of women who were screened every two years during their 50s and 60s versus those who were not. Note that this study did not include women in their 40s, the group in which routine mammography has been hotly debated in the U.S. (More on Time.com: Phony Cancers and Self-Inflicted Acid Attacks: A National Outbreak of Munchausen’s?)
Of interest, though, was the correlation between the availability of mammogram services and reduction in breast cancer death rates found in the study; this is likely due to a tertiary factor: the availability of mammograms indicates a healthy medical system that already targets women’s health.
As Healthland reported before, medical tests also increase your exposure to harmful radiation. Click here to find out how much radiation is emitted by medical imaging, including mammograms. One test may not have an overwhelming impact on your cancer risk, but it’s something to consider when weighing the risks and benefits of annual screening.
More on Time.com:
Study: Cancer Deaths Decline in Europe, but New Cases Rise
Photos: The Landscape of Cancer Treatment
Graphic: The State of Cancer