Answer provided by Dr. Christopher Ananian
Radiologists have always been cognizant of the fine line in imaging, weighing the risk versus the benefit of using ionizing radiation for the detection of cancers. While many modalities use radiation for imaging (X-Ray, CT, nuclear medicine imaging, and mammography), breast screening is carefully regulated by the Mammography Quality Standards Act (MQSA) to ensure that the radiation dose is as low as possible. Since the risk of radiation-induced cancers increases with the radiation dose, the MQSA maintains a tight regulation on the radiation exposure used with mammography and the radiologists are very careful to ensure the minimum number of images. To put this dose exposed to the breast tissue in prospective, the average effective dose from natural background radiation in the United States, excluding man-made and medical sources, is about 3 mSv per year. The average effective dose from two-view digital mammography is 0.4 mSv or approximate 7 weeks of natural background radiation.
Many studies have looked at the effect of radiation exposure and the development of cancer, with most of the data collected from following 76,000 Japanese atomic bomb survivors from Hiroshima and Nagasaki for over 50 years. Based on this information, the United States National Academy of Sciences Biologic Effects of Ionizing Radiation (BEIR) VII Group, which has estimated radiation risks to the U.S. population, and the International Commission on Radiological Protection (ICRP) have studied the relationship of radiation dose and the lifetime attributable risk (LARs) of radiation-induced solid cancers such as breast cancers. According to the BEIR VII study, an average glandular dose of 3.7 mGy for a two-view digital mammogram results in a lifetime risk of developing 1.3 cases per 100,000 women aged 40 at exposure and less than 1 case per million women aged 80 years at exposure. Since these studies assume a cumulative effect of radiation exposure, annual screening digital mammograms performed on women aged 40-80 is associated with a LAR of fatal breast cancers of 20-25 cases per 100,000 women screened.
In addition to the risk of radiation induced breast cancer, the benefits of breast imaging is also important to discuss. Breast cancer is the second leading cause of death in women with 1.3 million women diagnosed with breast cancer each year. One in 8 women will develop breast cancer over their lifetime with increased cancer development occurring with age. By age 40, one in 69 women will develop breast cancer, with that risk increasing to 1 in 27 women by age 70. One of the greatest factors in determining the severity and prognosis of breast cancer is early detection through annual screening mammography.
As radiologists, we are constantly weighing the benefits of imaging versus the risk of causing harm though the use of radiation. However, with annual mammographic screenings, the risk of possibly causing 20-25 cancers per 100,000 women pales in comparison with the number of cancers found and lives potentially saved through early detection. At Princeton Radiology, our mammographic units use a radiation dose well below the recommended MQSA levels of 3 mGy per image and even with tomograpohic (3-D) images, each view only results in a dose of 1.45 mGy in order to prevent unnecessary radiation exposure. Through the use of 3-D tomographic images, the need for additional images in order to work up breast findings is also significantly decreased. Additional imaging modalities which do not involve the use of ionizing radiation such as ultrasound and MRI, are also routinely used to work up breast abnormalities in order to decrease the potential radiation exposure. Annual screening breast ultrasounds are also used in women with dense breast tissue to further evaluate the breast without causing additional exposure. At Princeton Radiology, your radiologists are committed to providing the best imaging experience while always ensuring the safest practices are followed.