The Problem With Breast-Cancer Screenings

A new study finds that regular mammograms are not as effective as we thought. They could even be harmful.

WASHINGTON, DC - OCTOBER 24: The White House is bathed in pink light for National Breast Cancer Awareness Month October 24, 2013 in Washington, DC. October is observed as Breast Cancer Awareness Month every year, by public service groups, medical professionals and government agencies that combine to promote awareness of the disease. (Photo by Win McNamee/Getty Images)
National Journal
Sophie Novack
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Sophie Novack
Feb. 12, 2014, 6:25 a.m.

The gen­er­ally ac­cep­ted re­com­mend­a­tion of reg­u­lar breast-can­cer screen­ings in older wo­men just re­ceived a very heavy dose of skep­ti­cism.

A new study pub­lished in the Brit­ish Med­ic­al Journ­al on Tues­day found that reg­u­lar mam­mo­grams did not re­duce the death rate from breast can­cer. They did, however, lead to over­dia­gnos­is and treat­ment.

The Canada-based study is a large-scale, long-term, in-depth look at the im­pact of screen­ings we take for gran­ted as crit­ic­al to can­cer care. It ran­domly as­signed 89,835 wo­men, ages 40 to 59, to either a mam­mo­graphy group (an­nu­al screen­ings) or a con­trol group (no mam­mo­graphy) over a five-year peri­od. All wo­men in the mam­mo­graphy group and those 50 to 59 in the con­trol group re­ceived an­nu­al phys­ic­al breast ex­am­in­a­tions as well; those 40 to 49 in the con­trol re­ceived one phys­ic­al ex­am­in­a­tion fol­lowed by stand­ard care.

The study found that of the 44,925 wo­men in the mam­mo­graphy group, 666 in­vas­ive breast can­cers were dia­gnosed dur­ing the five-year screen­ing peri­od. Of the 44,910 in the con­trol group, 524 were dia­gnosed in this time. Of these, 180 in the mam­mo­graphy group and 171 in the con­trol group died of breast can­cer dur­ing the 25-year fol­low-up.

Over the course of the full study, 3,250 wo­men in the mam­mo­graphy group were dia­gnosed with breast can­cer and 500 died, com­pared with 3,133 dia­gnoses and 505 deaths in the con­trol group. Age did not ap­pear to have an im­pact.

The dif­fer­ence in death rate — 500 versus 505 — is not sig­ni­fic­ant between the two groups, but the dif­fer­ence in dia­gnos­is is. After 15 years of fol­low-up, the study found an ex­cess of 106 breast-can­cer dia­gnoses in the mam­mo­graphy group. Over­all, 22 per­cent of breast can­cers de­tec­ted by screen­ings were over­dia­gnosed.

Mam­mo­grams have long been pro­moted as the ne­ces­sary weapon to com­bat breast can­cer, the second lead­ing cause of can­cer death in wo­men. The Amer­ic­an Can­cer So­ci­ety cur­rently re­com­mends an­nu­al mam­mo­grams for wo­men age 40 and older. The Na­tion­al Can­cer In­sti­tute re­com­mends them every one to two years. The Susan G. Ko­men Found­a­tion, the largest, most well-known breast-can­cer or­gan­iz­a­tion in the U.S., in­cludes reg­u­lar screen­ings as a large part of its mis­sion.

However, the new study com­plic­ates this as­sump­tion. Over­dia­gnos­is can lead to un­ne­ces­sary, harm­ful, and ex­pens­ive treat­ment, and the tests them­selves in­clude small amounts of ra­di­ation that can be harm­ful in heavy doses.

While the find­ings do not ne­ces­sar­ily change these re­com­mend­a­tions, they raise ques­tions about the uni­ver­sal screen­ing pre­scrip­tion for what is clearly a pretty com­plex situ­ation.

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