Mammograms are used as a screening test for detecting breast cancer in women of all ages. The main goal of any cancer-screening test is to correctly identify people who have cancer. This is also called the sensitivity of the test.
A test that has the sensitivity of 90 percent means that 90 percent of people tested who truly have cancer are correctly identified as having cancer, and 10 percent are missed or misdiagnosed.
The sensitivity of a mammogram, according to Susan G. Komen, is 84 percent. What that means is a mammography correctly identifies about 84 percent of women who truly have breast cancer. Sensitivity is known to be higher among older women. A high sensitivity means few cases are missed when using the test.
The accuracy of a mammogram can depend on a variety of factors such as:
1)Breast Density
It is more difficult to interpret results for younger women due to the fact that breasts of younger women contain more glands and ligaments than those of older women. More glands means higher breast density which can obscure signs of cancer.
The reason sensitivity of a mammogram is higher among older women is because with age, breast tissue becomes fattier and has fewer glands, which makes it easier to interpret mammogram results.
2) Menopausal Hormone Therapy
Another factor that can affect accuracy of mammograms is menopausal hormone therapy. MHT increases the risk of breast cancer and increases the difficulty of reading mammograms because it causes an increase in breast density.
Results from the Women’s Health Initiative, a study cited on a Susan G. Komen web article on accuracy of mammograms, found that women who take MHT had breast cancer that was at a more advanced stage than women who did not take MHT.
This was found to be true in women taking estrogen as well as progesterone. Women who took either type of MHT (estrogen and progesterone, or estrogen alone) are found to have higher breast density, which can cause a need for additional follow-up testing.
3) The Type of Mammography Test Used
Digital mammography is found to have more accurate results than film mammography. This is due to the fact that digital images are viewed on a computer and can be lightened or darkened. Certain sections can be enlarged and analyzed more closely.
The fact that digital mammography allows you to control images on a computer can make digital mammography more accurate then film mammography.
In addition, "use of breast ultrasound has dramatically improved breast cancer diagnosis accuracy," when used in conjunction with mammography, according to Memorial Hospital Breast Center at University of Colorado.
According to the Susan G. Komen website, digital mammography is more accurate when finding breast cancer in women who:
1) Are premenopausal or perimenopausal
2) Are under age 50
3) Have dense breast tissue
For women who do not fall into one of those categories, film and digital mammography are found to be similar in their ability to detect breast cancer early on.
It is important to note that new mammogram guidelines from the American Cancer Society that came out on October 20, 2015, state that clinical breast exams, either from a medical provider or self-exams, are no longer recommended.
After reviewing data from numerous studies, ACS has determined that having more screening does not always produce findings that call for treatment. In fact, excessive mammogram screening can actually be harmful. The ACS found that clinical breast exams did not produce early enough breast cancer detection to benefit the patient.
Clinical breast exams could result in a false positive result that could lead to more unnecessary intervention. A false positive result occurs when healthy individuals are misidentified as having cancer.
The most important thing to do is use a screening tool, or a combination of screening tools that are best suited to your health needs. Open and honest communication with your health care professional will allow you to craft a health plan that will ensure your well-being.
Sources:
EmpowHER.com. ACS changed guidelines: how often should mammograms be done now? November 2 2015.
https://www.empowher.com/breast-cancer/content/acs-changed-guidelines-how-often-should-mammograms-be-done-now
Mayo Clinic. Tests and Procedures Mammogram. October 27 2015.
http://www.mayoclinic.org/tests-procedures/mammogram/basics/risks/prc-20012723
Susan G. Komen. Accuracy of Mammograms. October 27. 2015
http://ww5.komen.org/BreastCancer/AccuracyofMammograms.html
Susan G. Komen. Table 31 Digital Mammography vs. Film Mammography. November 2 2015.
http://ww5.komen.org/BreastCancer/Table31Digitalmammographyversusstandardmammographyforbreastcancerscreening.html#sthash.wz1RGgui.dpuf
University of Colorado Health Memorial Hospital. How accurate are mammograms? October 27, 2015.
http://www.memorialbreastcenter.org/how-accurate-are-mammograms
Reviewed November 4, 2015
by Michele Blacksberg RN
Edited by Jody Smith