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BREAST CANCER REVIEW

Detection and Screening

Introduction

The goal of breast cancer screening is to detect cancer at its earliest possible stage, before it causes symptoms. Since breast cancer is a progressive disease, early stage cancers are more likely to be treated successfully and with less aggressive treatment strategies. The main methods of screening for breast cancer are clinical breast examination, mammography, and breast self-examination. Their purpose is not diagnostic but to identify patients who warrant further evaluation.

Significance of Early Detection

For nearly two decades, the number of newly diagnosed cases of breast cancer has been increasing at an average of 0.3% a year.  At the same time, breast cancer mortality has been declining. Between 1990 and 2002, U.S. deaths due to breast cancer decreased 2.3% annually.¹ Studies show that breast cancer screening is responsible for as much as 46% of this decline, with the remaining proportion attributed to adjuvant treatments, such as chemotherapy and tamoxifen.²

Early detection and treatment is the key to surviving breast cancer. According to the American Cancer Society (ACS), when detected at a localized stage, the 5-year survival rate is as high as 98%. For regional disease, the rate is 86%. If the cancer has spread to distant organs, 5-year survival drops to 26%. Larger tumor size at diagnosis is also associated with decreased survival. Among women with regional disease and tumors less than or equal to 2.0 cm, the 5-year relative survival rate is 92%, whereas the rate associated with tumors 2.1-5.0 cm is 77%, and for tumors greater than 5.0 cm, 65%.³ Breast cancers found during screening examinations are more likely to be small and still confined to the breast.

A mammogram every 1 to 2 years can reduce the risk of dying from breast cancer by approximately 20% to 25% over 10 years for women aged 40 or older.⁴ Moreover, women whose breast cancer is detected by screening mammography are more likely to be adequately treated with less toxic therapy, such as breast conservation, and without chemotherapy.⁵ Despite these significant benefits, many U.S. women do not get regular mammograms. While individual reasons vary, concerns about screening costs and the expense of diagnostic procedures have been recognized as important barriers.

The Breast and Cervical Cancer Mortality Prevention Act of 1990

To help improve access to breast cancer screening for low-income, uninsured, and underserved women, Congress passed The Breast and Cervical Cancer Mortality Prevention Act of 1990, which created Centers for Disease Control and Prevention's (CDC) National Breast and Cervical Cancer Early Detection Program (NBCCEDP). This program provides both screening and diagnostic services, including clinical breast examinations, mammograms, pap tests, surgical consultation, and diagnostic testing for women whose screening outcome is abnormal. The text of the legislation that established the program, its amendments, and other directly related legislation can be found on the CDC web site.

The National Breast and Cervical Cancer Early Detection Program operates in all 50 states, the District of Columbia, 6 U.S. territories, and 12 American Indian/ Alaska Native organizations. In California, the program is facilitated by the California Department of Public Health Cancer Detection Programs: Every Woman Counts. Please refer to the CDS Programs section of this web site for more information.

Screening Guidelines

Guidelines for breast cancer screening are revised regularly to take into account new research findings and developments. The following are the recommendations of the ACS, updated in 2003.⁶

Clinical Breast Exam (CBE): Women in their 20s and 30s should have a CBE as part of a periodic health examination, preferably at least every three years. Asymptomatic women aged 40 and over should continue to receive a CBE as part of a periodic health examination, preferably annually.

Screening Mammogram: Women age 40 and older should have a screening mammogram every year and should continue to do so for as long as they are in good health.

Breast Self-Examination (BSE): Beginning in their 20s, women should be told about the benefits and limitations of BSE. The importance of prompt reporting of any new breast symptoms to a health professional should be emphasized. Women who choose to do BSE should receive instruction and have their technique reviewed on the occasion of a periodic health examination.^7,

Most expert groups endorse a triple approach to breast cancer screening. The combined use of clinical breast examination, mammogram, and breast self-examination is believed to offer the best opportunity for early detection.

Guidelines for Screening with Magnetic Resonance Imaging (MRI)

New evidence on breast Magnetic Resonance Imaging (MRI) screening has become available since the American Cancer Society (ACS) last issued screening guidelines in 2003. There is indication that MRI may be a useful adjunct screening method for certain high risk women.⁸ For more information, please refer to the ACS publication, American Cancer Society Guidelines for Breast Screening with MRI as an Adjunct to Mammography, in the March/April 2007 issue of CA: A Cancer Journal for Clinicians.

Clinical Breast Examination

Clinical breast examination (CBE) is the visual and manual examination of the breasts by a trained healthcare provider. CBE is typically performed at the yearly physical examination and preferably, on days 5-10 of the menstrual cycle. A comprehensive CBE includes a clinical history, visual inspection, examination of lymph nodes, palpation and pressure, patient education, and recommendations for follow-up. Proper documentation of all findings is crucial. The quality of CBE varies with the clinician's skill, experience and time spent performing the exam.

Clinical tools to assist providers with CBE have been developed by the California Department of Public Health. The following are available on this web site and are suitable for use in any clinic providing screening services:

• Breast Cancer History and Risk Assessment Form to help the clinician identify a woman's risk information and plan appropriate risk reduction strategies.
• Lymph Node Exam Guide for learning how to identify suspicious lymph node findings during routine breast cancer screening exams.
• Core Competencies of Clinical Breast Exam Card to review the important factors of a CBE.
• CBE Documentation Form for standardized, comprehensive documentation of breast health history, physical exam, results, and case management.

This web site also offers Breast Cancer Diagnostic Algorithms for Primary Care Providers (Cancer Detection Section, California Department of Health Services, 2005). Developed by an expert panel of California providers, the set of seven algorithms provides detailed guidance for the work-up of a new palpable mass; abnormal screening mammogram with normal CBE; spontaneous unilateral nipple discharge; breast skin changes; and breast pain. There is also a risk assessment algorithm and in the case of breast biopsy, an algorithm for the management of pathologic findings. 

Also available is a skills-based course for clinicians who provide breast cancer screening services. This course provides both didactic and experiential training and is offered at both training sites (CBE Course) and in physician offices (Office Detail Method). More information can be found in the CBE Training section of this web site.

Screening Mammogram

A screening mammogram is a low-dose x-ray of the breast used to detect breast changes in women who have no signs or symptoms of breast cancer. It is the most effective method for detecting breast cancer early.  Study findings of sensitivity are wide-ranging. Per NCI's Breast Cancer Surveillance Consortium, a range of 61.5% to 93.8% was determined from reports of more than 2.5 million screening mammograms (from 1996 to 2002).⁹ The average for all ages combined was slightly better than 79%.¹⁰

A standard screening mammogram consists of two views of each breast, the craniocaudal (CC) projection and the mediolateral oblique (MLO) projection. Additional views may be needed for women with breast implants. Screening mammograms allow for the detection of abnormalities that cannot be felt, such as calcifications. Both normal and abnormal findings are classified in accordance with the Breast Imaging Reporting and Data System (BI-RADS®).¹¹ The accuracy of mammography depends upon the skill of the technologist who takes the mammogram, the radiologist who interprets the mammogram, and the use of well-calibrated, dedicated equipment.

The Mammography Quality Standards Act (MQSA) of 1992

The regulation of mammography is outlined by federal law. The Mammography Quality Standards Act (MQSA) of 1992 requires that all mammography facilities in the U.S. (except those of the Department of Veterans Affairs) meet stringent quality standards, be accredited by the Food and Drug Administration (FDA), and be inspected annually. The FDA ensures that facilities meet standards which also apply to associated personnel (e.g., radiologists, radiologic technologists, and medical physicists). Additional information about MSQA and FDA-certified mammography facilities is available on the web site of the U.S. Food and Drug Administration.

Digital Mammography and Computer-Aided Detection

Efforts to improve mammography have resulted in the development of digital mammography and computer-aided detection. Both technologies are FDA-approved for use in breast cancer screening. 

Digital Mammography records x-ray images in computer code, as with a digital camera. Because digital images can be adjusted, subtle differences between tissues may be more easily noted than with conventional film. Digital images can also be stored and retrieved electronically, which makes long-distance consultations more efficient. Only facilities that have been certified to practice conventional mammography and have FDA approval for digital mammography may offer the digital system. The first digital mammography system received FDA approval in 2000. 

Computer-Aided Detection (CAD) involves the use of computers to bring suspicious areas on a mammogram to the radiologist’s attention. After initial review, digital images with highlighted areas are compared with the conventional mammogram to see if any of the highlighted areas require further evaluation. Research suggests that CAD may improve overall performance in detecting breast cancer at an early stage, although certain types of early cancer are not well detected by CAD (e.g., amorphous calcifications).

Breast Self-Examination

Breast self-examination (BSE) promotes a woman's familiarity with her own breasts so that she can readily detect changes and promptly report them to her healthcare provider. The principles of BSE are similar to that of CBE with respect to visual and physical examination. Typically, BSE is performed monthly, about a week after the start of a woman's period, and at the same time each month.

Lack of sufficient scientific evidence regarding the efficacy of BSE has prompted ACS and others to leave the decision of performing BSE to a woman's personal choice, stating that "it is acceptable for women to choose not to do BSE, or to do it occasionally."¹² At the same time, ACS emphasizes that "BSE heightens awareness of women to normal breast tissue, which makes it more likely for them to detect changes from normal."¹³  Many health professionals continue to consider BSE a valuable part of the screening triad for patients when they are taught the proper techniques. The clinical breast examination is an excellent opportunity for instruction. 

Any change in the normal appearance or texture of a woman's breast should be examined by a healthcare professional.

The most common signs of possible breast cancer are a new breast lump or mass, or thickening in or near the breast or underarm area.

Other signs and symptoms to watch for include a swelling of part of the breast; skin irritation, dimpling, or distortion; redness or scaling of the breast skin or nipple; nipple pain, inversion, rash or tenderness, or nipple discharge other than breast milk. Additionally, non-cyclical breast pain, which is relatively common and may occur for many reasons other than breast cancer, should always be brought to the attention of a health care provider.

Potential Harms Associated With Screening

In addition to the benefits associated with routine screening, ACS and others believe that women should be informed about its limitations and potential harms. Issues for providers to discuss with their patients include the following:

• False positives may require follow-up testing or invasive procedures such as breast biopsy to resolve the diagnosis. False positives can cause anxiety, inconvenience, discomfort, and additional medical expenses. Additional testing also poses additional risks.

• False negatives may provide false reassurance and/or delayed diagnosis. For example, a woman who receives a false-negative test result may delay seeking medical care even if she has symptoms.

• Overtreatment may be caused by screening mammograms that lead to medical interventions for certain cases of ductal carcinoma in situ (DCIS) that may not have needed treatment. Since it is not currently possible to predict which cases of DCIS will progress to invasive cancer, overtreatment is a potential harm associated with screening.

• Radiation exposure is a risk factor for breast cancer. Overall risk from single or cumulative diagnostic exposure from mammography is very small. However, risk increases with the amount of exposure and with exposure at younger ages. 

Despite these potential harms, most medical experts agree that breast cancer screening in accordance with recommended guidelines substantially increases the chances of early detection, and the benefit of early detection is decreased morbidity and mortality from breast cancer. Moreover, this benefit increases as women age. According to the U.S. Preventive Services Task Force, "[t]he absolute probability of benefits of regular mammography increases along a continuum with age, whereas the likelihood of harms from screening (false-positive results and unnecessary anxiety, biopsies, and cost) diminishes from ages 40 to 70."¹⁴ Studies conducted to date have not shown a benefit for regular screening mammograms, or for a baseline screening mammogram, in women under age 40.

Additional Screening Methods

When used with mammography, breast ultrasound and magnetic resonance imaging may enhance the effectiveness of breast cancer screening. 

Breast Ultrasound

Ultrasound is an imaging technique that uses high-frequency sound waves for examining tissues and internal organs. Its main application is to assist in the differentiation of solid masses from cystic lesions found by mammography or physical examination. It may also help with the detection of breast implant rupture or leaks. Additionally, it is often used to help guide a needle (fine needle or core) into a lesion.

Most recently, studies have demonstrated some value of breast ultrasound for detecting cancer among women with dense breast tissue, when used in combination with mammography. Additionally, ACS guidelines state that women known to be at increased risk for breast cancer may benefit from its use.¹⁵

Currently, ultrasound is not FDA-approved as a routine screening method for breast cancer. Limitations include its inability for detecting microcalcifications, equipment variability, lack of standardized exam techniques, lack of interpretation criteria and, per preliminary data, a substantially higher rate of false positives than mammography.¹⁶

Magnetic Resonance Imaging (MRI)

MRI uses magnets and radio waves to produce very detailed, cross-sectional images of the body. Compared to ultrasound, MRI is more sensitive for finding breast cancer. It has also been shown to detect more cancers than mammography alone. Additionally, for the detection of silicone implant leaks, MRI is considered the gold standard.

The high sensitivity of MRI has led to recent changes in ACS screening guidelines for certain high risk women. (For more information, please see Guidelines for Screening with Magnetic Resonance Imaging.) Concerns with MRI are similar to those with ultrasound; namely, its inability for detecting microcalcifications, equipment variability, and a lack of standardized exam techniques and interpretation criteria. Added concerns with MRI are its significant costs (about 10 times that of mammography) and limited availability.¹⁷ 

Newer and Emerging Methods

Research in the field of breast cancer screening is focused on increasing both the sensitivity and specificity of detection. Other methods currently being evaluated for their screening potential include breast fluid sampling (e.g., needle aspiration, ductal lavage, fine needle aspiration); nuclear medicine breast imaging (e.g., scintimammography, positron emission tomography); electrical impedance imaging; thermography; and optical imaging, among others.

The ACS web page Mammograms and Other Breast Imaging Procedures provides summary information about technologies currently under development for breast cancer screening. For more detailed discussion on this topic, see Mammography and Beyond: Developing Technologies for the Early Detection of Breast Cancer (Committee on Technologies for the Early Detection of Breast Cancers, 2001), available for Online reading at the National Academies Press web site.

Notes

¹American Cancer Society. Breast Cancer Facts & Figures 2005-2006. Retrieved Apr. 16, 2006 at: http://www.cancer.org/docroot/STT/content/STT_1x_Breast_Cancer_Facts__Figures_2005-2006.asp

²WomensHealth.gov. Screening, Therapies Behind Drop in Breast Cancer Death Rates (Oct. 26, 2005). Retrieved Apr. 16, 2006 at: http://www.4woman.org/news/english/528768.htm

³See note 1.

⁴Centers for Disease Control and Prevention. Breast Cancer and Mammography Information (last reviewed, Feb. 03, 2006). Retrieved Apr. 18, 2006 at: http://www.cdc.gov/cancer/nbccedp/info-bc.htm

⁵OncoLink Cancer News. Breast Cancers Detected by Mammography Require Less Toxic Therapy (Jan. 28, 2005). Retrieved Apr. 18, 2006 at: http://www.oncolink.com/resources/ article.cfm?c=3&s=8&ss=23&id=11508&month=01&year=2005

⁶A comparison of breast cancer screening guidelines by major review groups is available from National Guideline Clearinghouse (NGC). See NGC's Guideline Synthesis: Screening for Breast Cancer (last modified, May 1, 2006). Retrieved Apr. 25, 2006 at: http://www.guideline.gov/ Compare/comparison.aspx?file=BRSCREEN11.inc

⁷For years, ACS recommended monthly breast self-examination for women age 20 and older. In 2003, ACS's guidelines were updated and BSE became optional. See Role Of Breast Self-Examination Changes In Guidelines (May 15, 2003). Retrieved Apr. 27, 2006 at: http://www. cancer.org/docroot/NWS/content/NWS_1_1x_Role_Of_Breast_Self-Examination _Changes_In_ Guidelines.asp

⁸American Cancer Society. American Cancer Society Issues Recommendation on MRI for Breast Cancer Screening (March 28, 2007). Retrieved Apr. 1, 2007 at: http://www.cancer.org/docroot/MED/ content/MED_2_1x_American_Cancer_Society_Issues_ Recommendation_on_ MRI_for_ Breast_Cancer_Screening.asp?sitearea=MED

⁹Breast Cancer Surveillance Consortium. Performance Measures for 2,585,218 Screening Mammography Examinations from 1996 to 2002 by Age & Time (Months) Since Previous Mammography. Retrieved Apr. 1, 2007 at: http://breastscreening.cancer.gov/data/performance/ perf_age_time.html

¹⁰Breast Cancer Surveillance Consortium. Performance Measures for 2,585,218 Screening Mammography Examinations from 1996 to 2002 by Age. Retrieved Apr. 1, 2007 at: http://breastscreening.cancer.gov/data/performance/perf_age.html

¹¹The American College of Radiology Breast Imaging Reporting and Data System (BI-RADS®) is a classification system for standardizing mammographic reporting. ACR has developed BI-RADS® for ultrasound and MRI reporting as well. The BI-RADS® Atlas is available on the ACR web site at: http://www.acr.org/SecondaryMainMenuCategories/quality_safety/BIRADSAtlas/BIRADS Atlasexcerptedtext.aspx

¹²American Cancer Society. Updated Breast Cancer Screening Guidelines Released (May 15, 2003). Retrieved Apr. 27, 2006 at: http://www.cancer.org/docroot/NWS/content/NWS_1_1x_ Updated_ Breast_Cancer_Screening_ Guidelines_Released.asp

¹³See note 6.

¹⁴See note 6.

¹⁵National Guideline Clearinghouse. ACS Guidelines for Breast Cancer Screening: Update 2003 (last modified, May 1, 2006). Retrieved Apr. 25, 2006 at: http://www.guideline.gov/summary/summary. aspx? doc_id=3745&nbr=2971

¹⁶Smith RA, Saslow D, Andrews K. American Cancer Society Guidelines for Breast Cancer Screening: Update 2003. CA Cancer J Clin. 2003 May-Jun;53(3):141-69. Retrieved Apr. 27, 2006 at: http://caonline.amcancersoc.org/cgi/reprint/53/3/141.pdf

¹⁷See note 16.

Revised: November 30, 2007.

Source URL: http://qap.sdsu.edu/education/bcrl/Bcrl_detectscreen/bcrl_detectscreen_index.html

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