The following article is by Boone Hospital Center Radiologist Terry Elwing, MD.
Breast cancer affects all of us.
One in eight women will develop breast cancer sometime during her life. We cannot prevent it and the cause remains unknown.
However, through screening we can find cancers early, when they are curable.
Mammography remains the test of choice for breast cancer screening. It is cost effective, low risk, widely available and has a low false negative rate. False positive exams do require additional evaluation, which is usually limited to additional views and ultrasound, but might require a biopsy.
Dedicated breast imaging began in the late 1960’s, and screening mammography was first recommended in the late 1970’s. Many advances in screening have occurred over the past forty years with some of the most exciting occurring in the last ten years. The American Cancer Society and American College of Radiology recommend screening for all women with mammography to begin at age 40 and continue yearly.
There is much proof of benefit for annual screening of all women above 40 years, with studies showing up to 25 percent mortality reduction related to screening. There is no proof of benefit for self breast exam, yet we see many cancers detected by this means and continue to recommend annual physical exam by a health care provider in addition to monthly self breast exams.
Recent advances in mammography include the use of digital imaging techniques, computer aided detection and soon to be available tomosynthesis. Digital mammography has been shown to be better at cancer detection for women with dense breasts, but is also easier to perform and interpret.
Digital images can be analyzed with computer assistance and this acts as a second reader calling the radiologists attention to areas of mass density or calcification that might signify a cancer.
Tomosynthesis is in the final approval stages from the FDA and will soon be available. This technique will allow for a more in depth look at the breast tissue by reconstructing the digital data into many small slices through the breast.
We plan to combine this technique with a traditional mammogram. The exam time will be the same; there will be no additional radiation and little increase in cost. The biggest change will occur with interpretation, with potential advantages of fewer callbacks and better characterization of masses.
In addition to the advances discussed above, risk stratification has come to the forefront in mammography screening. The majority of cancers occur in women with no family history, but those who fall into high-risk categories may have lifetime risk for developing breast cancer as high as 50-60 percent, with the average risk women at 12 percent.
Some risk factors are well defined while others require much more investigation. Women who fall into the high-risk category include those with known genetic mutations, those exposed to high dose chest wall irradiation at a young age, those with a personal history of premenopausal breast cancer.
In addition to these women, there are many others who may have one or more family members with breast cancer, have personally had breast biopsies who may also be at increased risk.
We perform a risk assessment on every woman who gets a mammogram using the Gail Risk Model, which takes into account age, hormone status and history, family history of breast cancer, and personal history of breast biopsy.
There are other factors that cannot easily be measured, but we now have studies that show there is significant increased risk for breast cancer development in women who have mammographically dense breast tissue.
We have known for years that cancers were harder to detect in these women, but we know they are also more common in this group of women. Any woman with a Gail score of 20 percent or greater, mammographically dense tissue and Gail score of 15 percent or greater, and other known high risk women should be considered for additional screening with breast MRI.
Breast MRI detects cancer based on blood flow and lesion characterization. It will detect invasive breast cancer at a smaller and earlier stage that mammography, but does not qualify as a screening test that can be applied to the population in general.
It is much more expensive, invasive, time consuming and less widely available when compared to mammography. It also doesn’t detect some of the small noninvasive cancers that may only be seen on mammography as calcifications. Therefore it is not a substitute for a mammogram, rather a diagnostic aide or a screening tool for those of high risk.
High-risk women should begin screening earlier that those of average risk. This should be done annually with both mammography and MRI, staggering the exams every six months. Women in this category should begin screening between the ages of 25-30 years. The cancers found in this group of women tend to be more aggressive and occur at a younger age than the women of average risk.
As we look to the future, there is hope for prevention, but for now we will continue screening to detect cancers at an early stage, when most curable.
The introduction of tomosynthesis should allow us to detect additional cancers with mammography and we continue to work on risk stratification models that help to determine who will benefit from additional high risk screening and counseling.