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.
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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
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"Every Woman Counts, Every Year"
A perfect card for health providers to send to
women to remind them it’s time for their yearly breast cancer
screening.
Available in 5 languages from
The California Dept. of Health Services Cancer
Detection Section web site.
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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.
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Clinical
Breast Examination
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A comprehensive CBE includes:
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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:
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.
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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
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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).
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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.
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The most common signs
of possible breast cancer:
-
a new breast lump or mass
-
thickening in or near the
breast or underarm area
-
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
- nipple discharge other than breast milk
-
non-cyclical breast pain
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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.
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The benefit
of early detection is decreased morbidity and
mortality from breast cancer.
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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.
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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)
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| Color-enhanced slide shows magnetic
resonance image (MRI) of individual breast. |
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
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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.
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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.
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