A New England Journal of Medicine article casts doubt on the value of screening mammography in preventing death from breast cancer. (Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence, November 22, 2012, pp 1998-2005).
Screening mammography, or mammography performed in the absence of symptoms, has doubled the frequency of detection of early-stage breast cancer, from 112 to 234 cases per 100,000 women each year. However, the rate at which women have presented with advanced breast cancer has only slightly declined, by 8 cases per 100,000 women. This suggests that many of the cancers detected by mammography are not aggressive, and would never lead to symptomatic disease. Detection of these inactive cancers represent overdiagnosis, the discovery of cancers that would not cause illness. The authors estimate that in 2008, breast cancer was overdiagnosed in over 70,000 women, representing 31% of all diagnosed breast cancers. In the last three decades, breast cancer overdiagnosis has affected over one million women.
Mammograms are painful, and expose the woman to radiation which itself may cause breast cancer. Abnormal mammograms nearly always lead to biopsy, and, if cancer is detected, surgery followed by radiation and hormone suppressive therapy, and sometimes chemotherapy.
Influential vested interests, applying the fear factor, have strongly promoted yearly mammography for all women starting at the age of 40. This point of view may not be valid, and may lead to massive overtreatment and associated side effects and complications.
Two years ago it was recommended that PSA screening for prostate cancer be discontinued, after it was found that many prostate cancers do not progress, and will never be lethal. The natural history of breast cancer, especially ductal carcinoma in situ (DCIS), may be the same. The most effective recommendation for breast cancer screening may be an evaluation of patient lifestyle and family history, with mammography reserved for those at apparent higher risk. On the other hand, palpable breast masses and breast pain should be evaluated with mammography.