When to Have Mammograms: No Consensus

by Berkeley Wellness  

Two decades ago, the words “mammogram” and “annual” were almost inseparable and were usually followed by “starting at age 40.” Since then, expert groups have issued conflicting sets of guidelines about breast cancer screening for women at average risk, with some recommending a more limited schedule of mammograms in order to lessen the likelihood of false alarms and overtreatment. Where does this leave women? Just as men need to discuss the pros and cons of PSA screening with their doctors, women should do the same thing regarding when and how often to have mammograms.

Note: “Screening” means testing people at average risk, with no symptoms or signs of the disease.

The need for shared and informed decision-making was made evident by a research letter in 2017 in JAMA Internal Medicine, which found that doctors advise a variety of screening schedules, often picking and choosing among the recommendations from leading expert groups. Here’s a recap of what those recommendations are (current as of April 2019):

  • The U.S. Preventive Services Task Force, which helps set national standards for preventive care, advises mammograms every two years between the ages of 50 and 74. Women in their forties may also opt for biennial screening, depending on their risk factors and preferences. The Task Force offers no advice for women over 75 because research is lacking.
  • The American College of Physicians, in guidelines released in April 2019, agrees with the Task Force about women between ages 50 and 74 having mammograms every two years, and about women in their forties discussing the pros and cons of screening with their doctors.
  • The American Cancer Society (ACS) says for women ages 40 to 45, annual mammograms are optional. It advises annual screening between ages 45 and 54; biennial screening for ages 55 and older (though women may choose to continue annually), continuing as long as a woman has a life expectancy of at least 10 years.
  • The American College of Obstetricians and Gynecologists (ACOG) has long advised annual mammograms starting at age 40, with no upper age limit. But in 2017 it released new guidelines making screening optional for women in their forties and giving women the option of annual or biennial screening. After age 75, the decision to stop or continue screening should be based on a shared decision-making discussion, it now says.

Women at higher cancer risk because of family history or other factors may need earlier screening, all of the groups advise.

The JAMA Internal Medicine study surveyed a national sample of 871 primary-care physicians and gynecologists. It found that they were fairly evenly divided about which set of guidelines they said they trusted most. Not surprisingly, gynecologists were more likely to go with the longstanding ACOG guidelines, and doctors favoring ACS or ACOG were much more likely to advise screening women in their forties and those over 75. Contrary to the Task Force’s guidelines, most doctors recommended annual screening, four out of five advised screening for women in their forties, and two out of three advised it for women over 75. (It's not known if the newer, more relaxed ACOG guidelines will encourage more women and their doctors to forgo annual screening.)

Bottom line: All of the guidelines agree that women should start discussing mammography with their doctors (or other health care providers) at about age 40. Keep in mind that when it comes to cancer screening, more isn’t always better. Excessive screening greatly increases the risk of over­diagnosis and overtreatment without—from a public health perspective—saving enough extra lives to compensate for these harms. The guidelines of the Task Force and ACS are reasonable, but women need to work with their doctors to come up with the most suitable screening schedule for them, based on their values, preferences, and risk factors.

Also see Mammogram Advice: A Moving Target and Cancer Screening: It's Your Decision.

Originally published July 2017. Updated April 2019.