Current guidelines from the American Cancer Society recommend yearly screening for women age 45-54. Starting at age 55, the recommendation changes to once every two years. Women younger than 45 should be able to obtain screening if they wish. The United States Prevention Services Task Force (USPSTF) has slightly different criteria. They recommend that women in the 40’s NOT necessarily have yearly mammograms and carefully weigh the risks while women age 50-74 should have the procedure every two years. The more cautious position is likely due to two reasons:
1) The inaccuracy of test results in younger women
2) The risks involved in premature testing
The risks of radiation exposure are often downplayed or not clearly communicated to patients. One single bi-lateral screening can create a lifetime risk of cancer in 1.3 to 1.7 persons per 100,000.[ii] Age seems to play a critical role. For example, breast tissue of women under 40 years of age is highly sensitive to radiation. In fact, according to the Hong Kong Observatory, during reproductive life, the female breast may be one of the more radiosensitive tissues of the human body.
Digital mammograms are now an option in at least 95% of cases. They don’t necessarily increase exposure unless more images are taken. The diagnostic mammogram is done when a suspicious occurrence needs further scrutiny. In lieu of that, more images are generally needed to obtain views from different angels which increases overall exposure. And it is not uncommon for a diagnostic mammogram to be ordered immediately after a screening mammogram.
The standard, 2D, two view mammogram emits roughly .7 millisieverts of radiation. The 3D mammogram takes pictures of thin slices of breast tissue from different angles. They tend to emit radiation levels at about twice the standard 2D, 2 view method, or 1 mSv, depending on the age of the machine. As a comparison, a chest x-ray emits approximately .08 mSv of radiation (about 100 times less). Although exposure seems to be much less, you may have heard that you should limit chest x-rays when possible. And on a further note, heart tissue, large veins, and muscle cells tend to be radioresistant, whereas breast tissue is considered radiosentitive.
The average person acquires roughly 4- 6 mSv of radiation per year, 3 mSv of that via background radiation and 1-3 mSv via man-made radiation. Those that habitat at higher elevations receive roughly 1 mSv more per year than those at sea level. The radioactive elements in our food and water contribute about .3 mSv per year. If you live in an area where radon gas is present, it can contribute 2 mSv to your overall annual exposure.
The current federal and state regulations limit radiation workers' doses to 0.05 Sv/year (50 mSv/year). The limit for the unborn child of a female radiation worker is 0.005 Sv (5 mSv) per 9- month gestation period. For the general public, the limit is 0.001 Sv/year (1 mSv/year), with provisions for a limit of 0.005 Sv/year (5 mSv/year) under special circumstances. The public dose limit is set at least 10 times lower than the occupational limit to give the public an extra margin of safety. A factor of 10 is also used for public protection in other industries.[iii] In 1994, a lifetime maximum exposure limit was specified by the Occupational Health and Safety Administration to be age x 10 mSv.
According to Clark University, there is strong evidence that breast cancer may be associated with exposure to ionizing radiation. How ironic is it that the device developed to save us from cancer may actually increase our tendency to develop it? Ionizing radiation has been labeled a carcinogen, even www.cancer.org states that repeated x-rays have the potential to cause cancer. A survey of patients noted the following:
· 42% stated that they had received no explanation or insufficient explanation of risks & benefits of a mammogram
· 28% were unsure about or disagreed with the statement that the mammogram’s benefits out way the risks
· 58% were unwilling to accept more radiation in exchange for higher diagnostic accuracy.
With the increase in radiation exposure in recent years, it would be prudent to strive to limit exposure whenever possible and to order imaging involving radiation only when perceived benefit would outweigh potential risk. All women, especially younger women, should consider getting a thermogram either in addition to or in lieu of the mammogram. The latter test is invasive, emits no radiation, and can detect abnormal tissue (inflammation) many years before a mammogram would.