Between 1980 and 1982, these guidelines expanded to advising a baseline mammogram for women aged 35-39 years; that women consult with their physician between ages 40 and 49; and that women over 50 have a yearly mammogram.
Between 1983 and 1991, the recommendations were for a baseline mammogram for women aged 35-39 years; a mammogram every 1-2 years for women aged 40-49; and yearly mammograms for women aged 50 and up. The baseline mammogram recommendation was dropped in 1992.
Between 1997 and 2015, the stakes were upped, and women aged 40-49 years were now recommended to have yearly mammograms, as were still all women aged 50 years and older.
In October 2015, the ACS changed their recommendation to say that women aged 40-44 years should have the choice of initiating mammogram screening, and that the risks and benefits of doing so should be discussed with their physicians. Women aged 45 years and older were still recommended for yearly mammogram screening. That recommendation stands today.
Controversies arise over risk/benefit
The technology was not, however, universally embraced. “By the late 1970s, mammography had diffused much more widely but had become a source of tremendous controversy. On the one hand, advocates of the technology enthusiastically touted its ability to detect smaller, more curable cancers. On the other hand, critics asked whether breast x-rays, particularly for women aged 50 and younger, actually caused more harm than benefit.”2
In addition, meta-analyses of the nine major screening trials conducted between 1965 and 1991 indicated that the reduced breast cancer mortality with screening was dependent on age. In particular, the results for women aged 40-49 years and 50-59 years showed only borderline statistical significance, and they varied depending on how cases were accrued in individual trials.
“Assuming that differences actually exist, the absolute breast cancer mortality reduction per 10,000 women screened for 10 years ranged from 3 for age 39-49 years; 5-8 for age 50-59 years; and 12-21 for age 60=69 years,” according to a review by the U.S. Preventive Services Task Force.9
The estimates for the group aged 70-74 years were limited by low numbers of events in trials that had smaller numbers of women in this age group.
Age has continued to be a major factor in determining the cost/benefit of routine mammography screening, with the American College of Physicians stating in its 2019 guidelines, “The potential harms outweigh the benefits in most women aged 40 to 49 years,” and adding, “In average-risk women aged 75 years or older or in women with a life expectancy of 10 years or less, clinicians should discontinue screening for breast cancer.”10
A Cochrane Report from 2013 was equally critical: “If we assume that screening reduces breast cancer mortality by 15% after 13 years of follow-up and that overdiagnosis and overtreatment is at 30%, it means that for every 2,000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings.”11