Breast MRI

Breast Cancer: The Sobering Statistics

Consider the following facts about breast cancer:

  • Women who live in North America have the highest risk of breast cancer in the world.
  • The American Cancer Society estimates that in 2008 about 182,460 new cases of invasive breast cancer will be diagnosed in the United States alone.1
  • Breast cancer is the second-most common cancer affecting American women, surpassed only by skin cancer.
  • Breast cancer is the second-most common cause of cancer death among women, surpassed only by lung cancer.

Given what’s at stake, it is imperative that physicians utilize the best available diagnostic tools to ensure early diagnosis and effective treatment.

Breast MRI’s Emerging Role in Cancer Diagnosis

Magnetic resonance imaging (MRI) has opened new doors for the evaluation and treatment of breast cancer. So how can MRI be worked into a diagnostic algorithm that for decades has relied only on physical examination, mammography, and ultrasound?

For a long time, mammography and ultrasound have been the diagnostic mainstays of breast evaluation. Mammography also has been an invaluable tool in the fight against breast cancer, reducing the mortality rate anywhere from 8 percent to 65 percent. It is widely available, relativelyinexpensive, and fast – making it a good test for screening purposes.


Ultrasound of the breast provides a real-time examination without any radiation, making it ideally suited for evaluating known or palpable breast masses. Its use in screening has been highly questionable, however, and ultrasound has limited usefulness in women with dense breasts. Moreover, its dependence on the skill of the technologist can make ultrasound an unreliable examination.


How Does Breast MRI Work?

MRI is an imaging modality that uses a microwave and a magnet to estimate the distribution of fat and water in the breast. Because it is not densitydependent and emits no radiation, this type of exam is well-suited for use with the breast.

During the examination the patient lies face-down on the MRI table. First, precontrast images are obtained. Next, a gadolinium contrast agent is administered and the breast imaged every minute or so to see the “angiogenesis,” or vascular behavior, of the tumor.

The sequential contrast-enhanced images allow the radiologist to analyze the rate of peak enhancement and “wash-out.” In other words, how fast does the mass take in the contrast and how fast does it release it? These factors are central in distinguishing benign from malignant tumors. Because of angiogenesis and leaky vessels, malignant breast tumors take in a great deal of contrast very quickly; they also release it very quickly. In benign masses the opposite effect is observed: the contrast is taken up gradually and consistently for several minutes.

A computer-aided detection, or CAD, system can aid the radiologist in localizing the areas that take in more contrast more quickly, using an automated process that creates color-coded maps of the areas of enhancement (see above right).

Integrating Breast MRI into the Diagnostic Algorithm

As we’ve seen, breast MRI is a powerful diagnostic tool and its role in breast imaging is steadily expanding. Today its use is indicated in five clinical situations:

  • Screening high-risk women
  • Evaluating indeterminate cases, especially with dense- or small-breasted women
  • Preoperative staging
  • Evaluating response to treatment, especially to allow for lumpectomy rather than mastectomy
  • Screening and evaluation of women with cancer symptoms and breast implants

Breast MRI’s Role in Cancer Screening

Breast MRI has unquestionable value in screening women at high risk for breast cancer. In several studies, the sensitivity of breast MRI for invasive cancer actually has approached 100 percent, proving to be a dramatically more effective tool than mammography for screening this population. In high-risk women, mammography has a sensitivity of only 0 percent for ductal carcinoma in situ (DCIS) and 6 percent for invasive cancer, compared to MRI’s sensitivity of 87 percent for DCIS and 90 percent for invasive cancer.4

The research on this topic recently prompted the American Cancer Society (ACS) to revise its screening guidelines to include breast MRI for high-risk women (see table below). The ACS now recommends screening breast MRIs for all women who have:

  • A lifetime breast cancer risk of 20 to 25% or greater
  • A strong family history of breast or ovarian cancer
  • A history of treatment for Hodgkin’s disease
  • Undergone multiple scoliosis surveys as children (in some cases)

Subtracted contrast-enhanced axial image shows multiple small enhancing masses in the anterior right breast (arrow). This represents multifocal cancer found in a patient with known right breast cancer.

American Cancer Society Recommendations for Breast MRI
Screening as an Adjunct to Mammography5

Recommend annual MRI screening (based on evidence):

  • Tested positive for BRCA gene mutation
  • First-degree relative of BRCA gene mutation carrier, but untested
  • Lifetime risk of 0 to 5% or greater, as defined by BRCAPRO or other models that are largely dependent on
    family history

Recommend annual MRI screening (based on expert consensus opinion):

  • Radiation exposure to chest between ages 10 and 30 (such as scoliosis surveys)
  • Li-Fraumeni syndrome and first-degree relatives of people with the syndrome
  • Cowden and Bannayan-Riley-Ruvalcaba syndromes and first-degree relatives

Insufficient evidence to recommend for or against MRI screening:

  • Lifetime risk of 15 to 0%, as defined by BRCAPRO or other models that are largely dependent on family history
  • Lobular carcinoma in situ (LCIS) or atypical lobular hyperplasia (ALH)
  • Atypical ductal hyperplasia (ADH)
  • Heterogeneously or extremely dense breast on mammography
  • Women with a personal history of breast cancer, including ductal carcinoma in situ (DCIS)

Recommend against MRI screening (based on expert consensus opinion )

  • Women with less than 15% lifetime risk

The false-positive rate of breast MRI has been cited as a concern by many clinicians. Studies have shown that, as criteria are refined and experience is gained, the specificity of breast MRI has increased significantly over the past several years. Today it ranges between 75 and 9 percent.6 The false-positive rate is highly variable between studies, with many as low as 4 to 5 percent and others measuring 3 to 4 percent.

However, with the increasing use and availability of MRI-guided breast biopsy, those lesions seen only on MRI can be biopsied to identify the false positives, rather than resulting in unnecessary open biopsies or unjustified changes in surgical intervention. At ProScan Reading Services, the radiologists’ combined experience of reading more than 10,000 breast MRI cases has helped to reduce our patients’ biopsy frequency by 5 percent.

Preoperative Evaluation of Women with Newly Diagnosed Breast Cancer

Breast MRI has tremendous potential to curb recurrence rates when used preoperatively. In one recent study, for example, a comparison was made between a group of 1 1 women with breast cancer who had preoperative MRI and 5 women with breast cancer without preoperative MRI.

At follow-up exams approximately 40 months later, the group without preoperative MRI had an in-breast recurrence rate of 6.5 percent and contralateral follow-up cancers in 4 percent. In contrast, the percentages for the group who had preoperative breast MRI were 1. percent and 1.7 percent, respectively.6

This not only establishes that breast MRI can curb recurrences, but also suggests that what is traditionally considered to be “in-breast recurrence” is not likely a recurrence, but rather unrecognized foci of cancer that were synchronous with the index tumor.7

The roles of preoperative breast MRI include:

  • Assessment of index tumor size
  • Detection of synchronous breast cancers in the contralateral breast
  • Detection of multifocal or multicentric disease in the ipsilateral breast
  • Evaluation of response to chemotherapy

Contrast-enhanced subtracted axial image shows large enhancing metastatic right axillary lymph node (arrow)

Monitoring Tumor Response to Treatment

Breast MRI also has high specificity in evaluation of tumor response to neoadjuvant chemotherapy. Traditionally, index tumor size changes after chemotherapy have been measured using clinical examination, ultrasound, or mammography.Unfortunately, these modalities suffer from a lack of sensitivity, often overestimating the amount of residual disease, and not showing changes in size until several cycles of chemotherapy have been completed.8

Several studies have highlighted the accuracy and sensitivity of breast MRI in this situation, allowing more objective and precise measurement of tumor response using the RECIST (Response Evaluation Criteria In Solid Tumors) criteria. For example, one study demonstrated that MRI could accurately identify patients who had no response to chemotherapy with a sensitivity of 100 percent and specificity of 85 percent after one cycle of chemotherapy, and 90 percent after two cycles.8 Determination of response is based mainly on size criteria, in conjunction with alterations in dynamic contrast enhancement. Response to treatment can also be used to determine if a patient is a candidate for a lumpectomy.

Using MRI in Patients with Breast Implants

More than one million American women have breast implants today. Possible complications may include leakage, rupture, infection, fibrosis, and contraction. Although mammography has been traditionally used to detect extracapsular rupture, it is insensitive to small leaks and intracapsular ruptures. The sensitivity and specificity of MRI for implant rupture were measured to be 76 percent and 97 percent in one study.9

The ability of MRI to detect carcinomas in women with breast implants is also extremely important. Mammography in women with implants is performed using modified compression imaging, which can increase the radiation dose and, in rare cases, may even rupture the implant. Even with these techniques, it is estimated that silicone implants obscure from 22 to 83 percent of breast tissue on mammography.9 Because of its cross-sectional nature, MRI does not suffer from this limitation in patients with implants.

Sagittal inversion recovery water-saturated sequences shows a silicone implant wiht the "linguine sign" indicating intracapsular rupture.

Summary: When Should Breast MRI Be Used?

High-risk screening, especially in women over age 50

  • MRI is useful as an adjunct to mammography in women at high risk, those with dense breasts, and evaluation for recurrence in women with history of high-grade cancer.

Indeterminate cases

  • MRI is also useful in clarifying findings that are equivocal or disparate on physical exam, mammography, and/or ultrasound.

Dense-breasted women

Preoperative evaluation and staging

  • MRI is accurate at detecting index tumor
    size, ipsilateral and contralateral
    synchronous cancers, metastases, and
    chest-wall infiltration.

Response to chemotherapy

  • MRI is helpful in measuring a tumor’s
    reponse to chemotherapy and determining who can undergo a lumpectomy.

Implants

  • Evaluation for complications, such as
    rupture or infection
  • Screening for cancer

Reimbursement for Breast MRI

Medicare and most other commercial health insurers reimburse for breast MRI services when medically necessary; some insurers require authorization prior to examination. The following Current Procedural Technology (CPT) code must appear on the patient’s prescription and should be reported to the insurer when obtaining authorization:

77059 – Bilateral Breast, With or Without Contrast

An additional CPT code (0159T – Breast MRI Computer-Aided Detection), used to report analysis with CAD, may be included with a patient’s examination. This code is only reported if the radiologist determines that CAD analysis would be useful for a patient’s examination. It is unnecessary to report this code during the prior authorization process.

Note: Although there is a CPT code for unilateral breast imaging, our imaging protocol includes both breasts when evaluating for cancer.

Because breast MRI is used only for diagnostic purposes, and to screen patients at high risk for developing breast cancer, reimbursement for this examination is rarely denied by insurers. The following International Classification of Diseases (ICD-9) codes are often reported in conjunction with breast MRI. These codes may be useful in describing the clinical indications for your patient’s examination to health insurers:

  • 611.71 Pain in breast
  • 611.72 Lump/mass in breast
  • 611.8 Other specified breast disorder
  • 611.9 Unspecified breast disorder
  • 611.79 Symptoms breast discharge – other
  • 174.9 Cancer breast
  • 238.3 Breast neoplasm/uncertain behavior
  • 610.0 Fibrocystic breast disease
  • 610.1 Cystic breast
  • 611.1 Hypertrophy breast
  • 611.0 Inflammation disease of breast

Out-of-Pocket Patient Expenses

Although breast MRI is nearly always covered by insurance, most patients have at least some minimal coinsurance requirement. Breast MRI is an expensive examination and fee schedules can vary from provider to provider by hundreds of dollars for the same examination. Hospitals are typically the most expensive site of service for MRI examinations. What’s more, patients often receive separate bills from the hospital and the interpreting radiologist, leading to confusion and increased expense. Choosing the right facility for these services potentially can save your patient hundreds of dollars in out-of-pocket expense.

Selecting a Breast MRI Provider

Not every MRI facility is equipped to provide breast MRI services, and not every radiologist is qualified to render the specialized interpretations needed to make accurate use of this powerful tool. When referring your patients for breast MRI, we believe you should know the following:

Are other breast imaging modalities available?

Breast MRI is not necessarily a replacement for other breast imaging modalities, and in most cases is used in conjunction with mammography. Prior mammography may be necessary for comparison and may be easily obtained if the breast MRI provider did not perform these services initially. It is not necessary for a high-quality provider of breast MRI services to offer additional breast imaging modalities.

Does the radiologist have adequate experience in breast MRI interpretation?

Breast MRI examinations are highly complex; the interpreter must review as many as ,500 images per case, evaluating the anatomical features and structure of the breast, as well as the enhancing characteristics of the lesion that help differentiate between malignant and benign conditions. Our radiologists, in partnership with ProScan Reading Services, have read more than 10,000 breast MRI cases. The experience level of the interpreter largely determines how sensitive and specific the examination will be — and most importantly, the likelihood your patient will experience a false-positive finding and unnecessary biopsy.

References

  1. http://www.cancer.org/docroot/CRI/content/CRI_ _4_1X_What_are_the_key_statistics_for_breast_
    cancer_5.asp?rnav=cri (accessed online, 4/ /08).
  2. Berry DA, Cronin KA., Plevritis SK, et al. “Effect of Screening and Adjuvant Therapy on Mortality
    from Breast Cancer.” N Engl J Med 005; 353:1784-179 .
  3. Kolb TM, Lichy J, Newhouse JH. “Comparison of the Performance of Screening Mammography,
    Physical Examination, and Breast US and Evaluation of Factors that Influence Them: An Analysis of
    7,8 5 Patient Evaluations.” Radiology 00 ; 5:165-175.
  4. Bigenwald RZ, Warner E, Gunasekara A, et al. “Is Mammography Adequate for Screening Women
    with Inherited BRCA Mutations and Low Breast Density?” Cancer Epidemiol Biomarkers Prev 008;
    17:706-711.
  5. Saslow D, Boetes C, Burke W, Harms S, et al. “American Cancer Society Guidelines for Breast
    Screening with MRI as an Adjunct to Mammography.” CA Cancer J Clin, 007, 57:75-89
  6. Fischer U, Zachariae O, Baum F, et al. “The Influence of Preoperative MRI of the Breasts on
    Recurrence Rate in Patients with Breast Cancer.” Eur Radiology 004; 14:17 5-31.
  7. Fischer U, Friedemann B, Luftner-Nagel S. “Preoperative MR Imaging in Patients with Breast Cancer:
    Preoperative Staging, Effects on Recurrence Rates, and Outcome Analysis.” Magnetic Resonance
    Clinics of North America 006; 14:351-36 .
  8. Padhani AR, Hayes C, Assersohn L, Powles T, et al. “Prediction of Clinicopathologic Response of
    Breast Cancer to Primary Chemotherapy at Contrast-Enhanced MR Imaging: Initial Clinical Results.”
    Radiology 006; 39: 361-374.
  9. Berg WA, Nguyen TK, Middleton MS, Soo, et al. “MR Imaging of Extracapsular Silicone from Breast
    Implants: Diagnostic Pitfalls.” Am. J. Roentgenol. 00 ; 178:465-47 .

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