Is radiation exposure from mammograms dangerous?

The current recommendation is annual screening mammogram starting at age 40.  It is a well known fact that screening of asymptomatic women has been accredited for the decline in mortality of breast cancer.  Breast cancer is the most common form of cancer in women and the second leading cause of cancer deaths in American women.  In 2009, approximately 194,280 patients were estimated to be diagnosed with invasive breast cancer, and 62,280 with carcinoma in situ.  An estimated 40,610 would have died of this disease.  For a woman of average risk, the lifetime incidence of breast cancer is one in seven or 14%.

Yet, many women hesitate to have a mammogram due to the recent publicity of radiation exposure link to increased risk of cancer overall.  This risk should be placed in perspective.  Humans are exposed routinely to radiation from natural sources, such as radon and cosmic rays from space, food and water.  Living at higher altitude results in higher radiation, as well as frequent air travel.  Additionally, even our own bodies normally contain small amounts of naturally occurring radioactive elements, such as certain isotopes of potassium. 

The average annual radiation exposure from both naturally occurring and manmade sources for a person living in the United States is approximately 500 millirem or 5 mSv (milliSievert).  Below is an approximate estimation of radiation dose involved in common diagnostic procedures:  chest X-ray – 0.1 mSv, mammogram – 0.4 mSv, CT head – 2 mSv, CT chest 7 mSv, CT abdomen 8 mSv, CT pelvis 6 mSv, CT chest angiogram for pulmonary embolism workup – 15 mSv, coronary angiogram or cardiac catherization – 15 mSv, and PET scan – 8 mSv.  Thus, the radiation amount associated with one mammogram is approximately 10% of routinely accepted annual exposure dosage.

The National Academies of Science and the International Commission on Radiation Protection estimates an increase in cancer incidence of one new cancer in 1,000 people exposed to 10 mSv.  As an example, a patient has a CT and is exposed to 10 mSv.  That person’s lifetime risk of cancer attributed to the scan would be 1 in 1,000 or 0.1%.  In comparison, his or her lifetime risk of developing any cancer is 1 in 2.5 or 40%.  Therefore, the risk of radiation exposure should be balanced against the medical necessity of the x-ray itself.  In my opinion, the benefit of detecting early curable breast cancer with annual mammograms clearly outweighs the very small and remote risk of the radiation exposure.