Q&A: Breast MRI Shows Its Strength

The numbers are alarming: the American Cancer Society estimates that in 2004, more than 200,000 American women will be diagnosed with breast cancer and 40,000 will die from the disease. While x-ray-based mammography screening of women over 40 is recommended, guidelines eventually will change as diagnostic tools for breast imaging such as breast magnetic resonance imaging (MRI) and ultrasound are better understood throughout the clinical community.

Studies are further defining the role breast MR plays in the diagnosis and treatment of breast cancer. Just last month, a study published in the New England Journal of Medicine concluded that MRI may be better than mammography in detecting breast tumors in women who have a family history of or genetic predisposition to breast cancer. The findings came from Erasmus Medical Center in Rotterdam and suggest that MRI be used in addition to mammography for this group of patients.

In June, the International Breast MRI Consortium (IBMC) presented a study at the American Society of Clinical Oncology that said breast MRI is more than twice as effective as mammography in detecting the number and extent of breast cancer tumors. The first international, multi-site study of more than 1,000 women at 17 institutions in the United States, Germany and Canada discovered that out of the 428 women who had breast cancer, breast MRI detected additional cancerous lesions in 56 women, while mammograms detected additional lesions in only 17.

Mitchell Schnall, MD, professor of radiology and associate chair for research, department of radiology at the University of Pittsburgh Medical Center (UPMC) was principal investigator of the study. Schnall has helped expand breast imaging services at UPMC that now include digital mammography, ultrasound, MR and positron emission tomography. The center performs approximately five to six breast MRI scans on research protocols per week and about 25 to 30 clinically per week.

Health Imaging & IT spoke with Schnall about the state of breast MRI, its promise as a supplemental tool to mammography and its role in improving treatment options for women with a diagnosis of breast cancer.

Q: The International Breast MRI Consortium's study concluded that breast MRI is significantly better than traditional mammography in detecting the presence and extent of disease in patients diagnosed with breast cancer. What role does breast MRI play today in the diagnosis and treatment of breast cancer?

A: If one looks at the two major areas where MRI has been used at large, multi-center studies, one is our study that shows that in patients with breast cancer, it is important to understand the extent of disease to appropriately plan therapy. One of the things our study showed is that MRI is significantly better at looking at the extent of disease than mammography is within the breast. We believe that MRI has the potential to reduce the local recurrence rate for breast conservation therapy by as much as 5 percent. So in addition to looking at the extent of the disease, breast MRI has potential for looking at the other breast in women with cancer and screening women who are particularly at high risk for breast cancer.

Q: What patients are ideal candidates for breast MRI?

A: There are two populations of patients: patients who have a breast cancer diagnosis and patients who are at a particularly high risk for breast cancer. And it's not just women with a relative who has had breast cancer. There are other non-relative risk factors, such as a diagnosis of ductal carcinoma in situ (DCIS), diagnosis of atypical hyperplasia, radiation therapy for Hodgkin's disease as a child and carrying a breast cancer susceptibility gene.

The sensitivity for breast MRI in the detection of invasive breast cancers larger than 3 mm approaches 100 percent.

Q: Why is this so?

A: Mammography [presents] a projection image and it relies on subtle architectural findings and the visibility of calcifications to find cancer. Breast MRI really relies on the blood flow. We give [the patient] a contrast agent and watch an enhancement that the contrast agent causes. So the first thing is that it is not so sensitive to overlying adjacent breast tissue, such as mammography is. Therefore, you don't run into problems with a dense breast. The second thing is that the enhancement is typically pretty striking. These things make it relatively straight-forward to detect breast disease. The big challenge in MRI is making the cut off where you are going to [diagnostically] call enhancement that we see normally in women versus enhancement that is cancer-related.

Q: What are the advantages of breast MRI as a supplement to mammography, especially for high-risk women?

A: To find more cancer, and presumably if you find more, you find it earlier, giving women the best opportunity for a cure and surviving that cancer.

Is there a good understanding in the clinical community of what breast MRI can accomplish? Absolutely not, at least by what I see in terms of patients who are referred into our clinical practice, the kinds of things they are referred in for, and from my discussion with some of the community physicians who send patients to us in terms of what their expectations are and what we can actually provide.

Q: What are the limitations of breast MRI?

A: The key limitation right now is availability and availability of expertise. The second main limitation is the availability to do MR-guided biopsies. If you are going to start doing MR to detect lesions, you have to be able to sample them and guide their removal with MR. Interventions are not widely available or practiced so that's a significant issue as well.

Q: What is the potential of breast MRI to improve treatment therapies and save lives?

A: Another thing that MR has been proposed for, and there has been a lot of work out at the University of California, San Francisco pioneering this, is looking at the response to [breast cancer] therapy. Women with breast cancer and large tumors are often treated with chemotherapy before surgery. We like to know early on if chemo is working. It has been shown that MRI can detect very early in the therapy whether or not chemotherapy is working. In that situation, response to local therapy is fine. But in the average woman who presents even smaller breast cancer, mapping its extent is going to help to plan the surgical approach, and that is whether she is candidate for breast conservation therapy or whether she may need mastectomy.

Q: Does breast MRI have the potential to change and improve therapies used to treat breast cancer?

A: Yes, I think it will. I think in today's world it may change the kind of surgery some women get. It may also change the type of radiation therapy, particularly now that new, novel partial breast radiation techniques are coming out. It is such a precise tool to localize the tumor that I think down the road we might see the development of image- guided therapeutic techniques. Things like radio-frequency ablation, focused ultrasound ablation that really use the images as a guide to be able to ablate rather than remove breast tumors. Because MR is so exquisite in being able to show the extent [of breast cancer], I think that we may see that become a reality.

Q: Is any research underway to determine if women at high risk of breast should get more intense screening such as ultrasound and MRI? Is more research needed to make MRI a necessary supplementary diagnostic test for women with a diagnosis of breast cancer?

A: There is a lot of research going on in multiple venues. The American College of Radiology Imaging Network (ACRIN) just finished a [16-center] study looking at the contralateral breast question. There also are a number of small screening studies going on all throughout the world. I think that we need to continue to evolve our technology to get the best quality of images and better understand the interpretation criteria.

Q: Do technologies such as MRI and ultrasound have the potential to eventually change screening guidelines for women and breast cancer, such as those suggested by the ACR?

A: Absolutely. There is a lot of research that we have to do to sort out how to use these new technologies in a screening setting. It will likely be coupled to risk assessment and in vitro diagnostics [blood tests] to guide the imaging evaluation. Due to the complexity of studying screening, this will unfortunately take time and money to work out. Overall, I think the guidelines are going to change substantially as we go forward.

Q: According to the 2003 HIS Health Group's report on U.S. Breast Cancer & Gynecologic Oncology Markets, approximately 1.47 million women will undergo breast biopsy in 2004. How prevalent is breast MRI-guided biopsy at this point, and how will it alter and improve treatment alternatives for women with a diagnosis of breast cancer?

A: Probably not that available, but it is a critical component. Any time you are practicing breast MRI, you have to have the biopsy capabilities that are image-guided. Right now with MRI, they are only scattered throughout the country. For example, we are the only group in the Philadelphia area doing it. We have patients from as far as Annapolis and Northern New Jersey who come here if they have a finding and need to get a breast MRI-guided biopsy.

Q: What is the future of breast MRI?

A: I think the field has come a long way from being very divided to being more unified. Technically, I think higher and higher spatial and temporal resolution scans will continue to be done and [the technology] is going to continue to get better and better. I think clinically we are going to see greater penetration so that it becomes a ubiquitous study that will be available to all high-risk women to all breast cancer patients.