Dr Mai Brooks, Mai Brooks, Mai Brooks MD

Breast cancer is the most common form of malignancy in women and the second leading cause of tumor deaths in American women.  In 2011, approximately 232,620 patients are estimated to be diagnosed with invasive breast cancer and 57,650 with carcinoma in situ.  An estimated 39,970 would die of this disease.  For a woman of average risk, the lifetime incidence of breast cancer is about one in seven.

           The mortality rate from breast malignancy in the United States has decreased by 31% between 1990 and 2007.  Most of this success is attributed to screening mammogram.  Improved medical treatments have helped to a lesser degree.  As expected, the key to long survival after cancer diagnosis is to discover it early and then to eradicate it with surgical excision.  Once the cancer has spread, no amount of drugs can cure it.  In the case of breast cancer, the key to early detection is screening mammogram (and physical exam).

           The evidence for screening mammogram comes from several large studies from many European countries as well as the United States.  The largest randomized controlled trial was conducted in Sweden.  This result was recently published by author László Tabár and colleagues (Swedish Two-County Trial: Impact of Mammographic Screening on Breast Cancer Mortality during 3 Decades, in the journal Radiology, volume 260, pages 658-663, September 2011).  A total of 133,065 women aged 40-74 years were randomly assigned into a group invited to mammographic screening and a control group receiving the usual care.  After 29 years of follow-up, the study shows a 31% reduction in breast cancer mortality in women invited to screening.  The authors calculate that screening 300 women for 10 years prevents one death from breast tumor.  Many experts think that the benefit of screening mammography is even greater in women who actually undergo testing compared to those women who do not.  This is because in the large population studies like the Swedish report above, some women invited to screen did not have mammogram.  On the other hand, women not invited also had mammogram, but to a lesser degree.  

           Yes, it is true that sometimes screening mammogram can pick up some findings, which lead to biopsies, that turn out to be benign or just pre-cancer.  Yes, this would cause anxiety, discomfort, and would cost some healthcare money.  Critics call this “over-diagnosis”.  This is because we have no perfect test that can tell will absolute 100% accuracy in each person which mammogram finding is bad invasive cancer and which is not.  Screening mammogram can also find tiny cancers, that then get treated with surgery, maybe even radiation and anti-estrogen pills or chemotherapy.  Critics call this “over-treatment”.  This is because we have no perfect test that can tell will absolute 100% accuracy in each person which tiny cancer will kill without treatment, and which would be fine left alone.  But the bottom line is that despite these imperfections, screening mammogram still significantly saves lives.  The current recommendation still stands, and it is annual screening mammogram starting at age 40.  Each woman needs to decide for herself whether she wants to have a test proven to reduce breast cancer mortality by 31%, over the inconvenience of “over-diagnosis” and the possible side effects of “over-treatment”.