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Archived Issues of Radiology Rounds
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When Should Breast MRI Be Used?
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| Note: Updated issue available (April 2007) |
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- Women at high genetic risk for breast cancer or with ≥2 first degree relatives with breast cancer may benefit from MRI screening
- Breast
MRI is appropriate when results from clinical examination, mammography,
and ultrasound are inconclusive and the radiologist suggests its use
for further evaluation
- MRI
may be appropriate for evaluation of women with diagnosed breast cancer
to determine extent of disease or to monitor neo-adjuvant therapy
- MRI
is the best way to find occult breast cancer in a woman who presents
with metastatic disease thought to have originated in her breast
- MRI is appropriate if rupture of breast implants is suspected
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Although
MRI is a sensitive method for detecting breast tumors, there is, as
yet, no evidence showing that MRI screening saves lives, as has been
demonstrated for mammography. Furthermore, current treatment of most
patients whose cancers were detected by mammography screening or
palpation is so effective that relatively few die from this disease. In
those cases where treatment is not successful, it is usually due to
metastasis before detection, which can occur even when tumors seem
small when first detected. Therefore, finding a tumor earlier may not
necessarily result in a better outcome. In addition, MRI screening of
the general population would not only be extremely costly but would
also result in many women with benign lesions undergoing unnecessary
biopsy.
MRI Screening for High Risk Patients
Women who may benefit from MRI screening are those who are known to be
at high genetic risk for breast cancer (carriers of the BRCA1, BRCA2,
TP53, or PTEN genes) or who have two or more first degree relatives
diagnosed with breast cancer. These women often develop cancer at an
earlier age and have aggressive forms of cancer.
Mammography is quite effective, but not as sensitive in detecting
cancers in these women because they have dense breast tissue that can
sometimes hide a tumor on a mammogram, whereas MRI is virtually
uninfluenced by breast density. On the other hand, mammography can find
calcifications that can indicate an early cancer, and these cannot be
seen by MRI. In one study in a high risk population population, the
sensitivity of MRI for detecting all cancers was 71% (see box) and 80%
for detecting invasive cancers. Since some cancers are not detected by
MRI but can be seen by mammography, mammography as well as MRI is
advisable for screening this population. As with the general
population, there are no studies that prove that MRI screening of women
at high risk for cancer will save lives, but given their very high
level of risk, many feel that screening them with MRI is reasonable.
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Sensitivity and Specificity of Examinations for Breast Cancer in a High Risk Population*
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Clinical Examination |
Mammography |
MRI |
| Sensitivity |
18% |
40% |
71% |
| Specificity |
98% |
95% |
90% |
| *Women with genetic or familial predisposition to breast cancer |
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MRI demonstrates large cancer vascularity
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Women with Recently Diagnosed Breast Cancer
Women who have recently been diagnosed with breast cancer may benefit
from MRI because it shows more extensive disease than first detected in
about 20% of women. Therefore, without MRI, patients are at risk of
incomplete surgical removal of tumors and some will have to return for
further surgery after pathologic examination determines that the
margins were not clear.
MRI also detects the presence of a second ipsilateral cancer in about
10% of women with recently diagnosed breast cancer. There is, however,
a potential downside to MRI in evaluating these women because treatment
of two ispilateral tumors requires mastectomy. Modern therapy has
reduced the recurrence rates for women who undergo lumpectomy and
radiation without MRI evaluation to under 2% at 10 years. Clearly, some
women who may have had unsuspected additional foci of cancer were
successfully treated without requiring a mastectomy.
About 2% of women diagnosed with breast cancer will develop cancer in
the contralateral breast within a year and there is a subsequent risk
of 0.5-1% per year. MRI of the contralateral breast detects tumors in
about 5% of women with recently diagnosed breast cancer, even when
clinical examination and mammography are negative. Because simultaneous
cancer in the contralateral breast is associated with a high risk of
metastasis (16%) and fatality (7%), patients whose cancers are detected
early may benefit from prompt treatment.
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Magnetic Resonance Imaging - Unsuspected cancer detected by MRI alone (arrow)
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MRI to Monitor Neo-adjuvant Chemotherapy
In patients with more advanced cancers, neo-adjuvant chemotherapy is
often necessary to shrink the tumor before surgery. In these patients,
MRI is advised to measure the tumor before treatment, during, and after
neo-adjuvant chemotherapy. If MRI indicates that the chosen therapy has
not resulted in tumor shrinkage after a course of treatment, then an
alternative therapy may be selected.
Women with Conditions Not Amenable to Conventional Imaging
Women
who have had previous surgery for breast cancer, have silicone
implants, or have radiographically dense breasts may have inconclusive
results from clinical examination, mammography, and ultrasound. When
these conventional evaluation methods are inconclusive, the radiologist
will recommend an MRI if it is likely to provide more diagnostic
information. Breast MRI can distinguish between scar tissue and
recurrent cancer and its image quality is not significantly impaired by
dense tissue or implants.
Because MRI is more
sensitive for cancer than mammography, it is the method of choice in a
patient presenting with metastatic disease thought to be of breast
origin. In addition, MRI is the best imaging modality for
determining whether a silicone breast implant has ruptured, which may
be suggested by breast pain after trauma. |
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Scheduling
Breast
MRI is performed on the Main Campus in the Avon Breast Evaluation
Center, WACC219 , Mass General Imaging-Chelsea, Mass General West
Imaging - Waltham, and Mass General MRI in the Charlestown Navy Yard.
Examinations at all sites can be scheduled through the Radiology Order
Entry system, http://mghroe
or by calling 617-724-9729.
Further Information
For further questions, please contact, Daniel B. Kopans, M.D., Director of Breast Imaging in the Avon Breast Evaluation Center,
at 671-726-3093. We would also like to thank Michelle C. Specht,
M.D., Surgical Oncology, for her assistance and advice for this issue.
This article provided useful information about the appropriate use of imaging studies:
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References
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American College of Radiology (2004). ACR practice guideline for the performance of magnetic resonance imaging (MRI) of the breast. (Download .pdf)
Kriege, M, Brekelmans, CT, Boetes, C, Besnard, PE, et al. (2004) Efficacy of MRI and mammography for breast-cancer screening in women with a familial or genetic predisposition. N Engl J Med 351: 427-37
Liberman, L, Morris, EA, Dershaw, DD, Abramson, AF and Tan, LK. (2003) MR imaging of the ipsilateral breast in women with percutaneously proven breast cancer. AJR Am J Roentgenol 180: 901-10
Liberman, L, Morris, EA, Kim, CM, Kaplan, JB, et al. (2003) MR imaging findings in the contralateral breast of women with recently diagnosed breast cancer. AJR Am J Roentgenol 180: 333-41
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