Feature 0511

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MRI of the Breast - Feature 0511

MRI of the breast is a non-invasive imaging modality that has been gaining importance in the assessment of breast cancer. The extremely high sensitivity of Breast MRI has lead to its increased use as a tool to aid in the staging of breast cancer, in the detection of breast cancer, in the assessment of women at high risk of breast cancer and as a problem-solving tool.

X-ray mammography is the accepted standard screening test for breast cancer. The screening role of mammography is supported by its successful track record, wide availability, low cost and reasonable sensitivity. The modality is well entrenched and has proven itself effective in detecting breast carcinoma. The routine use of screening mammography has helped to save countless lives. When detected early, breast cancer has a cure rate of 95%. For this reason, early detection is imperative.

There are instances in which a test, other than mammography, may be either more effective or necessary to extract additional information. After a breast cancer has been detected, it is important to establish the amount of tumor involvement and the degree of tumor spread. MRI of the breast with gadolinium has an extremely high sensitivity in the detection of breast cancer. MRI can determine the size of the area of tumor involvement, the presence of additional (synchronous) lesions in the same breast, the blood flow characteristics of the tumor, the presence of enlarged lymph nodes and the presence of tumor in the opposite breast. Some breast tumor types, such as lobular carcinoma of the breast, are very difficult to assess with conventional mammography and have a tendency to occur bilaterally. MRI excels in the detection of these tumors.

MRI is not routinely used for breast cancer screening because of its higher cost. A breast MRI costs between $1,000 and $1,500. This is about 10 times the cost of a mammogram. Although the sensitivity (ability to detect a tumor) of breast MRI is higher than that of mammography, the specificity (ability to be sure that it is a tumor) remains somewhat problematic, resulting in a relatively high rate of unnecessary biopsies. Mammography also shares the specificity problem, but to a lesser extent.

A small percentage of the breast cancer population (5% to10%) has a genetic predisposition for breast carcinoma. Two mutated breast cancer genes have been described, BRCA1 and BRCA2. These are transmitted genetically to offspring family members. The chance for breast cancer in patients with these mutated genes increases with age and is estimated to be 50% by age 50. Women with these genes should be screened with MRI since they have a much higher incidence of breast cancer.

Another problematic area for conventional x-ray mammography is the assessment of the dense breast. Breast tissue differs in its consistency depending on the relative proportions of glandular tissue, fatty tissue and fibrous tissue. Younger patients tend to have a higher proportion of glandular tissue. This type of breast tissue results in a “dense” mammogram. Dense mammograms can hide cancerous tissue and have a higher incidence of missed cancers at mammography. MRI does not suffer with the problems of dense tissue. MRI can detect invasive carcinoma equally well in dense tissue or fatty tissue.

When a locally advanced beast cancer is found, breast conservation surgery may not be possible unless the tumor size is first reduced by chemotherapy. This is referred to as “neoadjuvant chemotherapy”. Breast MRI prior to neoadjuvant chemotherapy can define the size of the tumor and the blood flow pattern of the tumor (vascularity). Highly vascular tumors are more likely to respond to the neoadjuvant chemotherapy. After the institution of neoadjuvant chemotherapy, tumor size shrinkage is slow. Gadolinium enhanced MRI can assess the response to therapy earlier than any other method, by assessing the changes in the vascularity of the tumor. This can aid in the selection of the most effective chemotherapeutic agents.

MRI of the breast also finds a role in determining the presence of residual or recurrent tumor after surgery. At mammography, post surgical scar cannot be differentiated from recurrent tumor without serial mammograms. It may take two years or more to detect a slowly growing tumor recurrence. MRI offers a sensitive alternative. Several months after surgery, surgical scar stabilizes. The scar tissue does not enhance following gadolinium enhancement. Any residual or recurrent breast cancer will enhance, easily differentiating recurrent or residual tumor from scar tissue.

A proper MRI examination of the breast requires sophisticated MRI equipment, well-developed protocols, trained personnel and radiologist expertise. Not all MRI facilities can provide the necessary ingredients to perform good breast MRI. Radiology Associates of North Idaho, in conjunction with Kootenai MRI has the commitment, the trained personnel and the necessary state-of-the-art equipment to provide this service at a high level of quality and expertise.

Images:

Multi-focal right breast carcinoma demonstrating increased vascularity (click image to enlarge):
Left breast cancer (click image to enlarge):

Author
A. J. Martinez M.D.
Radiologist

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	Feature Highlight MRI is not routinely used for breast cancer screening because of its higher cost. A breast MRI costs between $1,000 and $1,500. This is about 10 times the cost of a mammogram. Website Information We provide the best and most up-to-date information on our website. However, it is important that you understand our web disclaimer. Also, you should always discuss your health issues with your physician.