Use of Magnetic Resonance Imaging in breast cancer screening
The use of Magnetic Resonance Imaging (or MRI) is not common with initial breast cancer screening. A carefully performed mammogram is much more convenient and economical, and is usually adequate to inform initial decisions as to whether a biopsy is warranted.
Mammograms often reveal the pretense of potentially pre-cancerous microcalcifications, but even with magnetic resonance imaging it is unlikely that a radiologist will be able to distinguish malignant from benign microcalcifications (The presence of microcalcifications alone might be a benign finding or might indicate a high-risk or early DCIS scenario).
However, if a mass or suspicious lesion of a significant size is evident, then breast MRI become a very sensitive and effective diagnostic tool.
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High sensitivity, low specificity
Though extremely sensitive, magnetic resonance imaging still has relatively low specificity. What that means is even though some abnormalities may be clearly visible, the ability to accurately predict exactly what those abnormalities are is quite limited (With increasing experience, however, radiologists are becoming more and more capable of specific interpretations). There is a real danger when relying exclusively upon magnetic resonance imaging of false positive findings, with the possibility of completely unnecessary surgeries as a result. MRI findings must be confirmed through biopsy before any treatment decisions are made.
Other conventional methods more useful in most cases
MRI is not used for asymptomatic patients with average risk. It is also not indicted for examination of microcalcifications, for inflammatory changes, or for ‘dense tissue‘ found at mammography in patients of average risk. Mammogram and follow-up ultrasound remain the best approach for routine screening, and a percutaneous biopsy is the most efficient follow-up for most indicators.
The major benefit of magnetic resonance imaging is also one of its drawbacks: it is able to detect lesions which are very very small (less than 10 mm) and allows you to view 70% more of a breast image than conventional methods.
This can lead to many unnecessary investigations. At screening, MRI can find many more “potential” lesions than mammography or ultrasound, but most of these turn out to be elements of normal tissue that are benign. In fact, the consensus opinion seems to be that women who are at ‘average‘ risk for breast cancer development should not be screened using MRI.
Magnetic resonance imaging is used for screening in certain situations
The most compelling use of MRI is for the detection of malignancy in discovered lesions or masses. It is frequently used for women with breast cancer implants. And, it is used to distinguish scar tissue from potential lesions in post operative patients. Most of the time, however, MRI is used for clinical staging purposes for patients with confirmed malignant neoplasia, especially in patients with dense breast tissue.
Magnetic resonance imaging is also frequently used for screening high risk patients with BRCA1 and BRCA2 genetic variants. Breast cancer screening with MRI is quite often now recommended for women who have an approximately 20-25% or greater lifetime risk of breast cancer development, and this would include women with a strong family history of breast or ovarian cancer, and women who were previously treated for Hodgkin disease.
Here are some common Q&A on MRI…
- When is MRI usually performed? It is performed after you have had a biopsy that’s positive for cancer, and your doctor needs more information about the extent of the disease. In certain situations, such as for women with high risk of breast cancer, breast MRI may be used with mammograms as a screening tool for detecting breast cancer.
- Why is MRI done? Breast MRI is most often used to screen for breast cancer in women thought to have a high risk of the disease. Your doctor may recommend a breast MRI if you’ve been diagnosed with breast cancer, and your doctor wants to determine the extent of the cancer, you have a suspected leak or rupture of a breast implant, you’re at a high risk of breast cancer (family history, etc), you have a strong family history of breast cancer, you have very dense breast tissue, and mammogram didn’t detect a prior breast cancer, and/or you have a history of precancerous breast changes such as atypical hyperplasia or lobular carcinoma in situ, a strong family history of breast cancer and dense breast tissue.
- What are some known risks for MRI? A breast MRI is a safe procedure that doesn’t expose you to radiation. But as with other tests, a breast MRI has risks such as a risk of false-positive results, or a risk of reaction to the contrast dye used.
- How do I prepare for my MRI appointment? Schedule your MRI for the beginning of your menstrual cycle, tell your doctor about any allergies you have, tell your doctor if you have kidney problems, tell your doctor if you’re pregnant or if you’re nursing, don’t wear anything metallic during the MRI, and tell your doctor about implanted medical devices.
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