Bilateral Whole Breast Sonography:
Ultrasound (sonography) uses sound waves to image the breast. Ultrasound does not require compression of the breast, nor an intravenous injection of contrast. Bilateral whole breast sonography has been extensively evaluated as a potential screening test. In women with dense breasts, screening ultrasound detects additional cancers to those discovered with digital mammography. The number of new cancers found, is similar to that seen with 3D mammography. Unfortunately, employing ultrasound as a screening tool increases the number of unnecessary biopsies to an unacceptable level (Ref. 2). For this reason whole breast ultrasound is not offered at Radiology Ltd as a screening test.
3D Mammography takes multiple x-ray images of the compressed breast using different projections, and from this data reconstructs multiple thin images representing the breast volume. These images are then dynamically viewed by your radiologist, one after another, like a movie. Tomosynthesis helps to increase the conspicuity of cancers by removing the layers of overlapping breast tissue that occur with conventional digital mammography. It is most effective in breasts of mixed density as we see in women with heterogeneously dense breasts (Illustration D). Tomosynthesis detects on average an additional 1.9 cancers per 1000 screens when used in addition to digital mammography (Ref. 3-5). To put that into context, screening digital mammography alone, detected 5.2 cancers per 1000 screens in the same studies. The use of tomosynthesis in addition to screening digital mammography does increase the radiation dose to the breasts by a factor of 2. The total combined dose however, is still below the U.S.Food and Drug Administration (FDA) radiation dose limits allowed for mammograms and is similar to the dose patients received before the introduction of digital mammography. The radiation dose of a digital mammogram examination is however negligible, being equivalent to that received from normal background radiation over a period of seven weeks.
Bilateral Breast Magnetic Resonance Imaging:
Breast MRI is our most sensitive tool for the detection of breast cancer. Across 9 scientific studies MRI detected an additional 11 cancers per 1000 screens in high risk women (Ref. 6). Its performance is not affected by breast density nor the presence of breast implants. It is not associated with x-ray radiation, however, MRI does require an intravenous injection of contrast.
Why do women need to know lifetime breast cancer risk in addition to breast density status to determine which, if any additional screening options are appropriate?
Although adjunctive screening may be appropriate for all women with dense breast tissue, unfortunately insurance considerations will play a role in which options are pursued for most women. When insurance companies decide if additional screening examinations will be covered for women with dense breast tissue, they often take into account lifetime risk for developing breast cancer.
Breast cancer risk assessment identifies the small percentage of women who are at high risk for breast cancer and may not be aware of it. At Radiology Ltd. all patients referred for screening have their breast cancer risk estimated using the Tyrer-Cuzick statistical model as part of our Personalized Breast Screening Service. Personal and family history, as well as numerous additional risk factors, are incorporated into the Tyrer-Cuzick model. A woman with a greater than or equal to 20% lifetime risk of breast cancer, is considered at high risk. This information is included in every screening mammogram report.