Breast cancer screening

A mammogram is the most common type of screening. It is an x-ray of the breast using a special machine. This test is done in a hospital or clinic and only takes a few minutes. Mammograms can find tumors that are too small to feel.

Mammography is performed to screen women to detect early breast cancer when it is more likely to be cured. Mammography is generally recommended for:

• Women starting at age 40, repeated every 1 to 2 years. (This is not recommended by all expert organizations.)
• All women starting at age 50, repeated every 1 to 2 years.
• Women with a mother or sister who had breast cancer at a younger age should consider yearly mammograms. They should begin earlier than the age at which their youngest family member was diagnosed.

Mammograms work best at finding breast cancer in women ages 50 to 74. For women younger than age 50, the screening can be helpful, but may miss some cancers. This may be because younger women have denser breast tissue, which makes it harder to spot cancer. It is not clear how well mammograms work at finding cancer in women age 75 and older.

This is an exam to feel the breasts and underarms for lumps or unusual changes. Your health care provider may perform a clinical breast exam (CBE). You can also check your breasts on your own. This is called a breast self-exam (BSE). Doing self-exams may help you become more familiar with your breasts. This may make it easier to notice unusual breast changes.

Keep in mind that breast exams do not reduce the risk of dying from breast cancer. They also do not work as well as mammograms to find cancer. For this reason, you should not rely only on breast exams to screen for cancer.

Not all experts agree about when to have or start having breast exams. In fact, some groups do not recommend them at all. However, this does not mean you should not do or have breast exams. Some women prefer to have exams.

Talk with your provider about the benefits and risks for breast exams and if they are right for you.

An MRI uses powerful magnets and radio waves to find signs of cancer. This screening is done only in women who have a high risk for breast cancer.

Women at high risk for breast cancer (greater than 20% to 25% lifetime risk) should have an MRI along with a mammogram every year. You may have a high risk if you have:

• A family history of breast cancer, most often when your mother or sister had breast cancer at an early age
• Lifetime risk for breast cancer is 20% to 25% or higher
• Certain BRCA mutations, whether you carry this marker or a first degree relative does and you have not been tested
• First degree relatives with certain genetic syndromes (Li-Fraumeni syndrome, Cowden and Bannayan-Riley-Ruvalcaba syndromes)

It is not clear how well MRIs work to find breast cancer. Although MRIs find more breast cancers than mammograms, they are also more likely to show signs of cancer when there is no cancer. This is called a false-positive result. For women who have had cancer in one breast, MRIs can be very helpful for finding hidden tumors in the other breast. You should do a MRI screening if you:

• Are at very high risk for breast cancer (those with a strong family history or genetic markers for breast cancer)
• Have very dense breast tissue

When and how often to have a breast screening test is a choice you must make. Different expert groups do not fully agree on the best timing for screening.

Before having a mammogram, talk to your provider about the pros and cons. Ask about:

• Your risk for breast cancer.
• Whether screening decreases your chance of dying from breast cancer.
• Whether there is any harm from breast cancer screening, such as side effects from testing or overtreatment of cancer when it's discovered.

Risks of screenings can include:

• False-positive results. This occurs when a test shows cancer when there is none. This can lead to having more tests that also have risks. It can also cause anxiety. You may be more likely to have a false-positive result if you are younger, have a family history of breast cancer, have had breast biopsies in the past, or take hormones.
• False-negative results. These are tests that come back normal even though there is cancer. Women who have false-negative results do not know they have breast cancer and delay treatment.
• Exposure to radiation is a risk factor for breast cancer. Mammograms expose your breasts to radiation.
• Overtreatment. Mammograms and MRIs may find slow-growing cancers. These are cancers that may not shorten your life. At this time, it is not possible to know which cancers will grow and spread, so when cancer is found it is usually treated. Treatment can cause serious side effects.

American Cancer Society website. Breast cancer early detection and diagnosis. www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection.html. Updated October 20, 2015. Accessed October 12, 2016.

American College of Obstetricians and Gynecologists (ACOG) website. ACOG statement on breast cancer screening guidelines. www.acog.org/About-ACOG/News-Room/Statements/2016/ACOG-Statement-on-Breast-Cancer-Screening-Guidelines. Updated January 11, 2016. Accessed October 12, 2016.

National Cancer Institute website. Breast cancer screening (PDQ®) - health professional version. www.cancer.gov/types/breast/hp/breast-screening-pdq. Updated July 29, 2016. Accessed October 12, 2016.

Siu AL; U.S. Preventive Services Task Force. Screening for Breast Cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med. 2016;164(4):279-296. PMID: 26757170 www.ncbi.nlm.nih.gov/pubmed/26757170.

Wolff AC, Domchek SM, Davidson NE, Sacchini V, McCormick B. Cancer of the breast. In: Niederhuber JE, Armitage JO, Doroshow JH, Kastan MB, Tepper JE, eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 91.