Key points

• This study sought to determine whether magnetic resonance imaging (MRI) could improve the ability to accurately diagnose the full extent of a patient's disease, including possible cancers in the opposite (or contralateral) breast at the time of the initial diagnosis. (Question 1)
• Investigators found that the vast majority of additional cancers can be found at the time of initial diagnosis if MRI is added to clinical breast exam and mammography as part of a thorough workup. (Question 3)
• 30 women in this study who were diagnosed with cancer in one breast, and determined by mammography and clinical breast exam to be cancer free in the opposite breast, had cancer in the opposite breast diagnosed by MRI. (Question 5)
• A variety of cancers were identified through MRI. In general, those cancers were at an earlier stage than cancers found in other types of exams, which usually improves outcomes. (Question 7)

1. Who is at risk and what was the purpose of this study?

Women who are diagnosed with breast cancer in one breast are at risk of having cancer in the opposite breast and not having it detected until after the first cancer has been treated. Some of these additional breast cancers can be identified by clinical breast exams or mammograms obtained during a women's diagnostic workup, but some cancers cannot be identified that way.

The study investigators sought to determine whether magnetic resonance imaging (MRI) could improve the ability to accurately diagnose the full extent of a patient's disease, including any possible cancers in the opposite (or contralateral) breast at the time of the initial breast cancer diagnosis.

2. Who conducted this study and how was it carried out?

This study was conducted by the American College of Radiology Imaging Network (ACRIN), a cooperative group sponsored and funded by the National Cancer Institute (NCI). The NCI component of the ACRIN Cooperative Group is administered by the Cancer Imaging Program within NCI's Division of Cancer Treatment and Diagnosis. The trial principal investigator was Constance Lehman, M.D., Ph.D., principal investigator of the ACRIN Breast MRI Trial, professor of radiology and director of breast imaging at the University of Washington and Seattle Cancer Care Alliance.

There were 25 recruiting sites in this study that encompassed a variety of clinical settings, from academia to private practice. Between April 1, 2003 and June 10, 2004, investigators enrolled 1,007 women with a recent diagnosis of cancer in one breast. In order to participate in the study, radiologists had to have interpreted a minimum of 50 breast MRI scans and performed at least 5 MRI-guided breast biopsies. 969 women completed the study.

3. How many women who have cancer diagnosed in one breast develop cancer in the other breast?

Previous research confirms that, over time, up to 10 percent of women who are diagnosed with breast cancer in one breast will eventually develop breast cancer in the opposite breast. The longer women are followed after a breast cancer diagnosis, the more likely they are to have cancer detected in the other breast. Investigators in this study found a resolution for this problem -- the vast majority of additional cancers can be found at the time of initial diagnosis if MRI is added to clinical breast exam and mammography as part of a thorough workup.

4. How soon after a diagnosis of breast cancer should a breast MRI be done?

The recommendation of researchers, based on these study results, is that MRI should be performed prior to treatment planning.

5. How many women in the study found out, by having an MRI, that they had cancer in the opposite breast that had not been detected by mammography or clinical exam?

Investigators sought to determine whether some of the cancers that develop after an initial diagnosis in one breast was made could instead be found at the time of this initial diagnosis. In this study, 30 women who were diagnosed with cancer in one breast, and determined by mammography and clinical breast exam to be cancer free in the opposite breast, had cancer in the opposite breast detected by MRI.

6. Was breast MRI better at finding cancers in some women than in others? Did age, whether a woman had reached menopause, or breast density affect whether mammography and clinical breast exam alone could effectively identify cancers?

Researchers thought that perhaps these factors would affect the ability of MRI to find cancers in the contralateral (or opposite) breast, but that was not the case. MRI proved equally beneficial for women regardless of menstrual status, whether their breasts had fatty or dense tissue, and for women with different types of breast cancers.

7. Were there certain types of cancer that breast MRI was more likely to find than mammography?

A variety of breast cancers were identified through MRI. In general, those cancers were at an earlier stage than cancers found in other types of exams, which is important because breast cancers detected at an earlier stage are often more treatable. Doctors want to find these cancers before they become invasive and spread to the lymph nodes. In this study, 60 percent of the cancers were invasive, and 40 percent were ductal carcinoma in situ (DCIS) -- an early tumor that has not invaded surrounding tissue. None of the cancers had spread to the axillary lymph nodes.

Lymph nodes are part of the lymphatic system, which carries waste products and other materials away from the cells. Lymph nodes filter this fluid before it returns to the blood stream and they also store white blood cells that help fight infection. Lymph nodes in the underarm are called the axillary nodes and are important in determining breast cancer stage and the likelihood that breast cancer has spread to other parts of the body. During surgery, some axillary nodes are removed to see if cancer cells are present.

8. Can MRI distinguish between different types of breast cancer?

Most common types of breast cancer originate in either the breast's milk ducts (ductal carcinoma) or lobules (lobular carcinoma). Some types, referred to as in situ, remain contained within their place of origin, while others become invasive, or infiltrating, and spread to surrounding tissues.

MRI can detect many early types of breast cancer, including some less common types. However, the cancer type is determined by the microscopic appearance of the cancer cells from a biopsy, and not from an MRI. Knowing what type of breast cancer a woman has plays a big role in selecting her treatment.

9. How might the study results minimize the emotional and physical toll on women due to breast cancer treatments?

For most women, the fear of a second cancer is quite high. Researchers hope that breast MRI can improve the quality of life, both at the time of a woman's diagnosis, and the years following. An MRI of the contralateral breast can provide women and their doctors with important information about whether there is cancer in that breast.

10. If a woman decides on having a double mastectomy, is there any benefit to her getting an MRI?

If the decision is made to have a double, or bilateral, mastectomy, the benefit of receiving an MRI is reduced. However, the MRI may still lead to more accurate information that would change the type of surgery performed or other treatment given before or after surgery. If a woman decides to have a single, or unilateral, mastectomy then the contribution of MRI is increased.

11. Should all women with an abnormal mammogram or clinical exam have an MRI exam?

No. MRI should not be used routinely in women with an abnormal mammogram or clinical exam. Benefits of MRI in this study were of women with a recently diagnosed breast cancer, not women with an abnormal mammogram or clinical exam.

12. Should women who were diagnosed and treated for breast cancer a number of years ago now get a MRI?

Use and practice of MRI is still being developed in the United States and no standard has been established. There is no consensus recommendation but women should consult with their physicians as a decision to use MRI may be based on the type of breast cancer, the treatment the woman received for her breast cancer, her age, and the density of her breast, among other factors.

The U.S. Preventive Services Task Force has not issued recommendations on use of MRI for breast cancer. The American Cancer Society formed a task force on MRI use for breast cancer and issued recommendations on March 28, 2007. Go to www.cancer.org for their recommendations.

13. Did breast MRI identify potential cancers that required biopsy but turned out not to be cancer?

Some participants did have biopsies for abnormalities which turned out not to be cancer (were benign), but the researchers found that the 88 percent specificity (the ability of a test to exclude the presence of cancer when it is truly not present) of MRI was significantly better than had been reported in other studies. In this study, 121 women, or 12 percent of participants, underwent a biopsy based on suspicious findings on the MRI and 3 percent had cancer diagnosed. That means 9 percent of participants underwent a biopsy for a benign condition that showed no cancer.

While MRI is a very powerful tool, it is not perfect. MRI will find cancers that are missed by mammography and missed by clinical breast exam, but it may also show suspicious areas that are not cancer. Doctors need to evaluate the MRI images carefully, use biopsies to diagnose suspicious lesions, and then treat those that do turn out to be cancer.

Additionally, this study also noted fewer false positives using MRI, or initial findings that later proved not to be cancer, than previous, smaller breast MRI studies had documented. The overall high accuracy of MRI to detect cancer in the opposite breast could be the result of improved technology or improved breast MRI interpretation. Further studies will need to be done to see if it's the technology or the interpretation that led to the high accuracy seen in this study.

14. Are researchers suggesting that MRI replace mammography in breast cancer screening?

This study was not designed to determine whether mammography or MRI is a better screening test for breast cancer in women who are at average risk. Mammography is an excellent tool for screening women at average risk for breast cancer especially because it is easily accessible and less expensive than MRI. The amount insurance companies pay for screening mammograms varies from $85 to $150, while the amount paid for MRI scans ranges from $ 800 to $ 2,000. The amount that a patient may pay for these screenings can vary considerably from these insurance payment amounts across the U.S.

The study results strongly support MRI as a complement to -- but not a replacement for --mammography. MRI improves the evaluation of the extent of disease in patients above and beyond what mammography can contribute. This finding suggests that patients who undergo a thorough diagnostic work-up, at the time of the initial diagnosis of a breast cancer, will benefit from having an MRI of the opposite breast to enhance that work-up.

15. Should all women who have breast cancer detected by mammography or clinical exam, and confirmed by a biopsy in one breast but not the other, have a breast MRI?

The results of this study support the recommendation of breast MRI to evaluate the contralateral breast of women with a current breast cancer diagnosis. The specificity (the ability of a test to exclude the presence of cancer when it is truly not present) and sensitivity (the ability of a test to detect cancer when it is truly present) demonstrated in this trial are very supportive of its use as an effective tool in more accurate diagnosis. MRI provides doctors with a more extensive evaluation of a breast, and may prevent women from having cancers in the opposite breast diagnosed years after the initial treatment of their breast cancer.

16. What is the impact on a women's prognosis if a breast cancer in the opposite breast is diagnosed years after the initial treatment of breast cancer?

Cancer can be diagnosed earlier when MRI is added to mammography and clinical breast exam. An earlier diagnosis, allowing for earlier treatment, is better.

17. If a woman has a negative breast MRI of the opposite breast, can she be assured that this breast does not have cancer?

There is no perfect imaging tool, but if a woman had a negative MRI in this study, the chance of her having a breast cancer diagnosed within a year was almost zero. Out of nearly a thousand women, three women who had an apparently negative, benign MRI were later determined to have cancer. The cancers that were identified were very small, non-invasive cancers called ductal carcinoma in situ (DCIS). Women who have a negative MRI can be reassured that the likelihood of significant disease in that breast is extremely small.

The very strong ability of breast MRI to show with near certainty that the opposite breast is cancer-free means that women can avoid some unnecessary mastectomies.

18. Where can women find a medical or imaging center that performs breast MRI?

Many imaging centers have established very effective breast MRI programs, and these are continuing to expand across the country. There is still not open access for all women in many parts of the United States to high-quality breast MRI. Women should speak with their doctors about the best place for them to undergo breast MRI if one is necessary.

Access for all women to high-quality breast MRI is very important. The American College of Radiology has a task force that is working to ensure that a woman, regardless of where she gets her breast MRI, knows that it is a high-quality scan. Work being done on new accreditation programs should significantly improve a woman's ability to receive a high-quality breast MRI.

19. Are all breast MRI scans similar?

There are many ways to perform breast MRI. It is important to have high-quality breast MRI computer software as well as scanners. Many factors, such as the timing of the scans, the type of scanner used, the injection of the contrast agent (a fluid used to enhance the breast images) into the veins of patients, and the methods of interpretation, currently can vary from site to site across the country. However, the diversity of medical facilities that participated in this trial, including institutions, community hospitals, and imaging centers, suggests that these results should be applicable to other practices.

20. Does insurance typically pay for MRIs of women with a recent diagnosis of breast cancer?

Some insurance companies provide reimbursement for breast MR imaging, and some do not. Many insurance companies have responded positively to prior research by reimbursing for breast MRI in high-risk women. Based on the results of this study, it is possible that more insurance companies will consider reimbursing women who have a current breast cancer diagnosis and undergo breast MRI. The American College of Radiology is working to help standardize reimbursement for this important test.

21. Does Medicare typically reimburse for MRIs for women with a recent diagnosis of breast cancer?

Medicare's national coverage policy for MRI states that MRI scans may be covered as diagnostic services if reasonable and necessary, and if performed on an FDA-approved model of MRI equipment. Local Medicare contractors have discretion to determine the circumstances under which a MRI scan is covered. Some contractors have selective coverage for MRI breast imaging, depending on patient diagnosis.

22. Given the cost of MRI, will the potential savings in patient care justify the cost of the additional exam?

In breast cancer detection, diagnosis, and treatment, the greatest costs come from treatment; the costs of treating breast cancer patients far outweigh the costs of imaging. An investment in breast MRI could decrease the cost of treatment. For example, thanks to early detection, women may have one surgery rather than two, or undergo fewer rounds of chemotherapy. Study authors are now conducting cost-effectiveness analyses to determine whether MRI, at the time of initial diagnosis, will provide savings because of more targeted, efficient, and effective treatment.

For a press release on using MRI to detect cancer in the opposite breast of newly diagnosed women, please go to http://www.cancer.gov/newscenter/pressreleases/MRIContralateralRelease.

Study information can be found at http://cancer.gov/clinicaltrials/ACRIN-6667

For more information about cancer, visit http://www.cancer.gov, or call NCI's Cancer Information Service at 1-800-4 CANCER.

ACRIN is an NCI-sponsored and funded clinical trials cooperative group made up of investigators from over 100 academic and community-based facilities in the United States, as well as several abroad. ACRIN's mission is to develop information through clinical trials of diagnostic imaging and image-guided therapeutic procedures that will result in the earlier diagnosis of cancer, allay the concerns of those who do not have cancer, and increase the length and improve the quality of life for cancer patients. ACRIN administration is headquartered at the Philadelphia office of the American College of Radiology and is under the leadership of Network Chair Bruce J. Hillman, MD, and Constantine Gatsonis, Ph.D the Network Statistician. The ACRIN Biostatistics Center is located at Brown University in Providence, RI. The NCI component of the ACRIN Cooperative Group is administered by the Cancer Imaging Program within NCI's Division of Cancer Treatment and Diagnosis.

The American College of Radiology (ACR) is a national professional organization serving more than 32,000 diagnostic radiologists, radiation oncologists, interventional radiologists, nuclear medicine physicians, and medical physicists, with programs focusing on the practice of radiology and the delivery of comprehensive health care services. Further information on the ACR can be found at www.acr.org.

Updated March 28, 2007

From  the National Cancer Institute