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Archived Issues of Radiology Rounds
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Screening Mammography - Who Needs It? What are the Benefits?
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With
all the controversy in the news in recent years, many women and their
physicians have been confused about the benefit of mammographic
screening for breast cancer. In fact, several very rigorous studies
have directly demonstrated the benefit of mammographic screening in
women over 40 and there has been a 20% drop in the death rate due to
breast cancer since 1990, which can be directly attributed to screening
mammography. From this information, we can conclude that mammography
screening aids in the detection of cancers at an early stage when they
have a better chance of being treated successfully.
While other imaging technologies have been found to be useful in
imaging breast tumors, including ultrasound, MRI, and PET, mammography
is the only modality that has been rigorously studied and validated as
a screening method. Research at MGH and elsewhere is directed towards
finding additional modalities to detect cancers at a time when they can
be cured. But, at this time, MGH radiologists feel that the data do not
support any referral for alternate imaging techniques for screening.
For detecting breast implant rupture, however, MRI has been shown to be
useful.
Recommendations for Screening Mammograms
The
National Cancer Institute, the American Cancer Society, and the US
Preventive Services Task Force (USPSTF) all agree that asymptomatic
women should start having annual screening mammograms at age 40. The
incidence of breast cancer increases steadily with age and there is no
clear cut-off age when mammography could not be beneficial. Since no
women over age 74 were included in the mammography screening trials,
the decision to continue screening in older women should be
individualized by considering the potential benefits and risks of
mammography in the context of current health status and estimated life
expectancy.
Annual screening mammograms are
recommended for:
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Asymptomatic women over 40 years
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Patients who have been successfully treated for cancer
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Women with 1st degree relative who has had breast cancer
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Women with a first degree relative (mother, sister, and daughter) who
has had breast cancer are considered to be at higher risk than the
general population and they should start screening earlier, at an age
10 years earlier than that at which the relative was first diagnosed.
Patients who have been successfully treated for cancer should continue
to be screened annually since they are at increased risk for a second
cancer. If a patient has had a mastectomy, then only the remaining
breast needs mammographic screening. Women who have been treated
conservatively, i.e. lumpectomy and radiation, should return to annual
screening as soon as breast compression can be tolerated (usually 6
months after completion of their therapy).
Breast
tissue has a very heterogeneous structure, which makes it very
challenging to accurately and consistently read mammograms. In order to
ensure the highest standards and to minimize missed diagnoses, two
radiologists independently review each mammogram at MGH. This extra
service increases the detection rate by 5-7%.
Mammography is not perfect and some cancers may not be visible due to
overlying dense tissue. Consequently, women over the age of 40 should
have at least an annual clinical breast examination and should be
encouraged to do breast self-examinations. Regular self-examination
helps women to become familiar with what is normal for them. Although
no clinical study has demonstrated that self-examination saves lives,
the woman herself finds most cancers that are not detected by
mammography.
Mammography Scheduling and Reporting
Mammography screening is performed in the Avon Comprehensive Breast Evaluation Center on the main campus at MGH, at Mass General West Imaging
in Waltham, and the MGH Health Center in Revere. Diagnostic imaging is
only available at the main campus. Mammography may be ordered online
via the Radiology Order Entry (ROE) system (http://mghroe
) or by calling 4-XRAY (617-724-9729).
Mammography reports are not available immediately after a screening
study, mainly because of the dual reading of mammograms. They are made
available to physicians online, usually within 24-48 hours. The patient
will be given the results of her diagnostic study before she leaves the
Center.
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(B) |
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(A) A small, non-palpable cancer is easily seen in fatty breast tissue.
(B) A large palpable cancer is hidden by the dense normal breast tissue
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Diagnostic Mammography
When
a potential abnormality is discovered clinically by the patient or her
doctor, the patient should be referred for mammography if she is aged
28 or older. In these cases, mammography can be considered both
diagnostic and screening, since the whole breast is examined for tissue
abnormalities.
At times, a patient is fearful that
the breast pain she feels is due to cancer, but this is rarely the case
and mammography is seldom helpful in depicting the cause of pain. Only
those with non-cyclic focal pain (from a single point), especially a
"drawing sensation," are in need of diagnostic imaging. Clinical
evaluation is more suitable in all other cases.
Clinical Symptoms of Breast Cancer:
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Lump |
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Nipple changes and/or discharge
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Skin retraction and/or thickening
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Focal, non-cyclic pain, especially a "drawing sensation" |
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Thickening
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Reporting Findings from Mammography
The
FDA now requires that radiologist’s reports end with an action oriented
code. This is based on the standardized reporting system devised by the
American College of Radiology (ACR). The ACR Breast Imaging Reporting
and Data System (BI-RADS®), based on the reporting format devised at
the MGH, standardizes the language used in mammography reports and
requires the use of the assessment categories. This reporting system is
intended not only to help clinicians understand the disposition of
their patients based on mammographic imaging but also to be an auditing
aid for mammography practices. The mammographic findings are
interpreted and assessed, using a categorical system that is intended
to convey the degree of concern and any pertinent recommendations for
follow-up mammography or biopsy.
BI-RADS Assessment Categories
Category 0
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Assessment incomplete - Need additional imaging evaluation
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Category 1
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Negative
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Category 2
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Benign Finding - e.g. cyst or fibroadenoma
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Category 3
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Probably Benign Finding - recommend follow-up mammography every six months for two years
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Category 4
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Suspicious Abnormality - biopsy should be considered
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Category 5
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Highly Suggestive of Malignancy - biopsy recommended
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Follow-up Imaging
Follow-up
mammography may be recommended by a radiologist when additional imaging
is needed or after an abnormal screening mammographic finding. In
addition, follow-up mammography may be recommended if there is a
question as to whether the correct tissue was removed during a biopsy
or surgery.
Follow-up imaging by other modalities
(ultrasound, MRI, CT) should be on the recommendation of radiologists
who specialize in breast imaging.
Further Information
For further questions on breast imaging, contact Daniel Kopans, M.D.
, 617-726-3093
Patient information on preparing for mammography at MGH
For general questions about web-based Radiology scheduling, call 617-726-0304
For general questions about Radiology Services, call 617-724-4902
BI-RADS reporting system
This article provided useful information about the appropriate use of imaging studies:
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References
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Kopans DB. (1994) Screening for Breast Cancer and Mortality Reduction Among Women 40-49 Years of Age. Cancer 74:311-322.
Kopans DB. (1999) The
Breast Cancer Screening Controversy and the National Institutes of
Health Consensus Development Conference on Breast Cancer Screening for
Women ages 40-49. Radiology 210:4-9.
Dershaw, DD. (2000) Mammographic screening of the high-risk woman. Am J Surg 180: 288-9.
Gui, GP, Hogben, RK, Walsh, G, A'Hern, R and Eeles, R. (2001) The
incidence of breast cancer from screening women according to predicted
family history risk: Does annual clinical examination add to
mammography? Eur J Cancer 37: 1668-73.
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Smith,
RA, Saslow, D, Sawyer, KA, Burke, W, Costanza, ME, Evans, WP, 3rd,
Foster, RS, Jr., Hendrick, E, Eyre, HJ and Sener, S. (2003) American Cancer Society guidelines for breast cancer screening: update 2003. CA Cancer J Clin 53: 141-69.
Tabar L, Yen MF, Vitak B, Tony Chen HH, Smith RA, Duffy SW. (2003) Mammography
service screening and mortality in breast cancer patients: 20-year
follow-up before and after introduction of screening. Lancet 361:1405-10
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