Benefits and Risks of Mammography
- Early detection of small breast cancers by screening mammography greatly improves a woman's chances for successful treatment. If breast cancer is caught and treated while it is still confined to the breast ducts (DCIS: ductal carcinoma in situ), the cure rate is close to 100%.
- Clinical studies in the U.S., Sweden, and the Netherlands have suggested that deaths from breast cancer could be cut by between 36% and 44% if screening mammography were performed annually on all women in their forties.
- The FDA reports that mammography can find 85 to 90 percent of breast cancers in women over 50 and can discover a lump up to two years before it can be felt.
- Breast cancers found by screening mammography of women in their forties were smaller and at an earlier stage (with less spread to lymph nodes or other organs) than cancers found in women not having mammography.
- Results reported by the American Cancer Society of the recent compilation of eight randomized clinical trials found 18% fewer deaths from breast cancer among women in their forties who had mammography.
Mammography is a special type of x-ray imaging that uses low dose x-ray; high contrast, high-resolution film; and an x-ray system designed specifically for mammography to create detailed images of the breast. Although breast x-rays have been performed since the 1920s, modern mammography has only existed since about 1970. Modern mammography systems use extremely low levels of radiation: usually about 0.1 to 0.2 rad dose per x-ray (rad is the scientific unit of measure of radiation energy dose).
To put mammography dose into perspective, a woman who receives radiation therapy as a treatment for breast cancer will receive several thousands rads. If a woman had annual screening mammography for fifty years (two x-ray views per breast), beginning at age 40 years and continuing until age 90, she will have received a total of 10 rads to 20 rads per breast over the course of 50 years.
The MQSA (Mammography Quality Standards Act) was created by the American College of Radiology (ACR) and passed by Congress to mandate rigorous guidelines for x-ray safety during mammography. The MQSA guidelines assure that mammography systems are safe and use the lowest dose of radiation possible. Patients should make sure they are being imaged at an ACR accredited facility using modern mammography systems.
Many women are concerned about the exposure to x-rays during mammography. However, the level of radiation used by modern mammography systems does not significantly increase the risk for breast cancer. Scientific data has shown that doses 100-1000 times greater those used for mammography are required to show any statistical increase in breast cancer frequency. There is no significant risk of radiation damage to breast tissue from mammography and the potential risk is greatly outweighed by the benefit of getting regular mammograms.
The quality of a mammogram is greatly dependent on compression of the breast, which may sometimes cause discomfort. However, the discomfort should be brief. Patients should feel firm pressure but no significant pain. If you feel pain, please inform the technologist. During the mammography examination, breast compression should only be applied two to four times per breast for a few seconds each. The entire procedure for screening mammography should take only 15 minutes to 20 minutes.
Breast compression during mammography is necessary in order to:
- Flatten the breast so there is less tissue overlap for better visualization
- Allow the use of a lower x-ray dose since a thinner amount of breast tissue is being imaged
- Immobilize the breast in order to eliminate image blurriness caused by motion
- Reduce x-ray scatter which also leads to image degradation
Some mammography facilities will allow the patient to control the breast compression herself during mammography. This can greatly reduce anxiety, making the woman feel more comfortable during the procedure, both physically and emotionally. Women should feel free to ask the technologist about controlling breast compression themselves before the exam begins or when scheduling the exam.
Click here to learn more about minimizing pain and discomfort during mammography.
In summary, the benefits of mammography for the early detection and treatment of breast cancer are very significant. The benefits far outweigh the minimal risk from radiation received during mammography and the discomfort that some women experience due to breast compression. If you experience significant discomfort during mammography, please discuss this with your mammography technologist.
Updated: November 28, 2009