Patient information: Breast cancer screening

BREAST CANCER SCREENING OVERVIEW

Cancer screening refers to the use of tests to detect cancer at an early stage, before it causes symptoms and hopefully at a time when it is curable. More than 200,000 women in the United States are newly diagnosed with breast cancer each year. About 40,000 women die each year of breast cancer, making it second only to lung cancer in cancer deaths among women.

The death rate from breast cancer has declined about 20 percent over the past decade [1]. This is due, in part, to the ability of increased screening to find the disease at earlier stages when the chances of successful recovery are higher. In fact, there is more scientific evidence supporting the use of screening tests for breast cancer than for any other type of cancer.

The information presented here is for women at usual risk of breast cancer. Women with a known genetic mutation, like BRCA1 and BRCA2, or who have several close relatives with breast cancer should (see "Patient information: Genetic testing for breast and ovarian cancer") for information about screening recommendations.

BREAST CANCER SCREENING METHODS

There are three main methods of screening for breast cancer: mammography, clinical breast examination, and breast self-examination.

Mammography — A mammogram is a breast x-ray. It is the best screening test for reducing the risk of dying from breast cancer. Early concerns about the radiation exposure from mammograms have lessened with the use of modern mammography equipment that exposes the breast to extremely low levels of radiation. The current level of radiation exposure is unlikely to significantly increase the risk of developing breast cancer.

The cost of mammograms is covered by most private insurances, Medicare, and Medicaid. The American Cancer Society has information about low cost mammograms that are available in most communities (1-800-ACS-2345).

Technique — Before the mammogram, patients are asked to undress from the waist up and wear a hospital gown. Each breast is x-rayed individually. The breast is flattened between two panels, which allows the radiologist to more easily see abnormalities. This can be uncomfortable, though the discomfort lasts for only a few seconds. Mammograms are most uncomfortable when done just before or at the beginning of the menstrual period; women should try to avoid scheduling their mammogram at these times, if possible.

Findings — The mammogram is interpreted by a radiologist. Sometimes the radiologist is present at the time of the mammogram; in these cases, a patient may be asked to wait a few minutes while the radiologist determines if additional x-ray views are needed. Having additional views does not necessarily mean that a cancer is present, but instead helps the radiologist to have the most accurate image. All mammography facilities are required to send results within 30 days and the woman must be contacted within five days if the mammogram is abnormal.

Breast cancer cannot be diagnosed by mammography alone. Women usually require further testing (eg, ultrasound or biopsy) if the mammogram shows a mass, new calcium deposits, or other abnormal findings. These findings do not always mean that a cancer has been found. One study found that 11 percent of mammograms performed in the United States require additional evaluation; the area in question was not cancer in more than 90 percent of these cases [2].

The abnormalities that radiologists typically look for on mammograms are calcifications and masses (figure 1 and figure 2).

• Macrocalcifications are large calcium deposits that most often represent degenerative changes in the breast such as might occur with aging or with previous trauma or inflammation. Macrocalcifications are common, particularly in women over the age of 50, and generally do not require a biopsy.
• Microcalcifications are small specks of calcium that sometimes suggest the presence of breast cancer. Depending upon the shape and pattern of microcalcifications, the radiologist may recommend a biopsy of the affected area or a repeat mammogram in three to six months.

Clinical breast examination — Clinical breast examination is peformed by a health care provider and is typically performed at the yearly physical examination. Healthcare providers usually inspect the breasts for any changes in size or shape and then palpate (feel) the breasts and the area under both arms for any change in texture or lumps.

Both clinical breast examination and mammography are important; studies show that about 50 percent of breast cancers found on screening were detected by both examination and mammography. Five to 10 percent are detected with examination and missed by mammography, and about 40 percent are detected by mammography and missed by examination.

Breast self-examination — Breast self-examination is a means of detecting changes in your own breasts. It typically is performed at the same time each month. The best time to perform breast self-examination is about one week after the menstrual period ends, when the breasts are least lumpy. In postmenopausal women who are not menstruating, the same day each month is recommended.

Most studies have not found breast self-examination to be beneficial in reducing the risk of dying from breast cancer. However, one large randomized trial found breast self-examination did result in women undergoing more breast biopsies for benign lumps [3]. Nevertheless, some women feel that practicing breast self-examination on a regular basis improves their ability to detect subtle changes that would otherwise not have been noticed. Breast self-examination is not a substitute for mammography or breast examination by a health care professional.

The studies suggest that performing breast self-examination correctly is important. Women who want to perform self-examinations should ask their health care provider to demonstrate how to do it and how to tell the difference between normal tissue and suspicious lumps. Instructions for performing self breast examination are provided here (table 1).

Breast MRI — Magnetic resonance imaging (MRI) uses a strong magnet rather than x-rays or radiation to create a detailed image of a part of the body (picture 1). Breast MRI may be recommended to aid in the diagnosis of breast cancer in selected situations [4]. MRI is not recommended to detect breast cancer in women who do not have a high risk of breast cancer because of the increased risk of a falsely positive result (when the MRI shows a suspicious mass that is not cancer). In addition, MRI is not as good as mammogram in detecting certain breast conditions, such as ductal carcinoma in situ.

BREAST CANCER TESTS

If an abnormality is seen on a mammogram or felt by the woman or her clinician, further testing is required to determine if cancer is present. One or more tests may be recommended, depending upon the woman's age, the location of the abnormality, and whether a lump can be felt.

Breast ultrasound — Breast ultrasound may be recommended if a mass is seen on mammography or felt during breast examination. The test uses sound waves to help determine if a breast mass is a simple cyst (fluid filled) or complex (fluid and tissue filled) or a solid tumor.

The risk of cancer is low if the mass appears to be a simple cyst based upon ultrasound; one study found no cancer in 223 simple cysts [5]. Masses that are complex or solid have a small risk of being caused by cancer.

Ultrasound is most useful in the following situations:

• To evaluate a palpable mass, particularly in women under age 35
• To evaluate a mass that is seen on mammography but cannot be felt

If the mass appears to be complex or solid, a breast biopsy is usually recommended.

Needle aspiration — Needle aspiration is a procedure that may be recommended to determine if a mass is cystic or solid. Needle aspiration is a reasonable option if the mass can be felt, is not too deep, or if ultrasound is not readily available or a tender cystic mass is suspected. that could be relieved by aspiration

It can be done in a healthcare provider's office, sometimes without anesthesia. The provider uses a needle and syringe to withdraw fluid from the breast mass. If the provider withdraws clear-colored fluid, the mass is unlikely to be cancer and usually resolves without further treatment. A follow up examination is recommended four to six weeks later to confirm that the mass has resolved.

However, if the fluid is bloody or if the provider is unable to withdraw fluid, the mass should be evaluated further (usually with a breast biopsy).

Breast biopsy — A breast biopsy may be recommended if an abnormal area is seen on mammography or if a mass appears to be complex (filled with fluid and tissue) or solid based upon ultrasound. The technique used to perform the biopsy depends upon the size and location of the abnormal area. Local anesthesia is usually given before the procedure to prevent pain. If the physician feels a lump, the biopsy can often be performed in the office by inserting a needle into the mass and withdrawing a sample of tissue.

If the abnormality is only found on the mammogram and the breast feels normal, the location of the biopsy must be guided with a mammogram or CT scan. The abnormality is visualized by the radiologist and its location is marked, often with a thin wire that is inserted through the skin. A surgeon uses the wire to know which area to remove.

The results of a breast biopsy are usually available within one week. If breast cancer is detected, further testing will be recommended. These issues are discussed in a separate topic review. (See "Patient information: Breast cancer guide to diagnosis and treatment".)

BREAST CANCER SCREENING RECOMMENDATIONS

Expert groups — All major North American expert groups recommend routine screening with both mammography and clinical breast examination for women ages 50 years and older. There is controversy about routine screening among women in their 40s, although over time, more and more groups are recommending screening for women in their 40s as well.

• The American Cancer Society, American College of Radiology, American Medical Association, United States Preventive Services Task Force, and American College of Obstetrics and Gynecology all recommend starting routine screening at age 40 years. The US Preventive Services Task Force and American Academy of Family Physicians recommends screening mammography every one to two years for women ages 40 and older [6].
• The American College of Physicians and The Canadian Task Force on the Periodic Health Examination recommend beginning routine screening at age 50 years.
• A 1997 National Institutes of Health Consensus Development Conference Panel Report on breast cancer screening in women ages 40 to 49 years recommended that women in this age group decide individually about breast cancer screening with their health care provider [7]. A 2007 guideline from the American College of Physicians makes a similar recommendation [8].

What is "routine" screening? — Most North American expert groups suggest that women over age 50 be screened every year. Groups that recommend screening for women in their 40s have tended to shift from recommending every one to two years to recommending a mammogram every year because there is concern about more rapid tumor growth in younger women.

There are no clear data on the effectiveness of routine screening mammography in women over age 70 years. Some researchers believe that mammography is less useful in these women because they have a reduced life expectancy and tumor growth is usually slower in older women. However, most expert groups recommend that routine screening should be continued as long as a woman has a life expectancy of at least 10 years because the risk for breast cancer increases as women age. The recommended interval for women over the age of 70 is one to two years, depending upon a woman's individual risk of breast cancer. (See "Patient information: Risk factors for breast cancer".)

The bottom line — All women should discuss the need for a mammogram with their clinician starting at age 40. Mammograms have the highest rate of detecting breast cancer. Virtually every well-performed study to date has found that screening mammography in women ages 50 and older reduces the risk of dying from breast cancer. A summary of trials found a 22 percent reduction in death of women in this age group who had regular mammography compared with women who did not [9]. For women in their 40s, the protection is somewhat less, both because breast cancer is less common and because cancer is harder to find with screening (examination and imaging tests) in younger women.

There are trade-offs between the benefits and risks of mammography in detecting the following:

• Breast cancers (that may end a woman's life prematurely)
• Precancerous lesions such as ductal carcinoma in situ (DCIS) (that often do not progress)
• False-positive results (that cause anxiety and potentially require unnecessary testing)

All women, especially those in their 40s, should discuss their situation with a health care provider and decide together when to start screening. Some useful information when considering mammography screening is presented in the figures (graph 1A-B). This figure shows what happens when 1000 women ages 40, 50, or 60 get annual mammograms for 10 years. It is possible to compare the number of women saved from death from breast cancer with the number of false-positive mammograms or diagnosis with a precancerous lesion (DCIS).

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Genetic testing for breast and ovarian cancer
Patient information: Breast cancer guide to diagnosis and treatment
Patient information: Risk factors for breast cancer

Professional Level Information:
Breast imaging: Mammography and ultrasonography
Epidemiology and risk factors for breast cancer
Genetic testing for breast and ovarian cancer
Primary care evaluation of breast lumps
Risk assessment and clinical characteristics of women with a family history of breast and/or ovarian cancer
Screening for breast cancer

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Cancer Institute

       1-800-4-CANCER
       (www.nci.nih.gov)

• National Comprehensive Cancer Network

      (www.nccn.com)

• American Cancer Society

       1-800-ACS-2345
      (www.cancer.org)

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• Susan G. Komen Breast Cancer Foundation

       (www.komen.org)