As part of our MBCC coverage we discuss MRI screening for breast cancer in patients who carry a BRCA mutation or have a first-degree relative who is a BRCA carrier.
Today, ahead of the Miami Breast Cancer Conference held in Miami, Florida, we are speaking with Sarah McLaughlin, MD, associate professor of surgery who specializes in breast cancer at the Mayo Clinic in Florida, about MRI screening for breast cancer, which she will be discussing at the conference.
-Interviewed by Anna Azvolinsky
Cancer Network: First, what are the current guidelines for breast cancer screening for women in the United States?
Dr. McLaughlin: The guidelines according to the American Cancer Society and the American College of Radiology recommend that women start receiving annual mammograms at the age of 40. The only exception to that would be women who have a first-degree relative who is diagnosed with breast cancer at an early age. Then they should begin screening 10 years prior to that. And of course those women at the highest risk for breast cancer, those with a genetic mutation like a BRCA1 or BRCA2 mutation, should be getting screened around the age of 25, with an annual MRI until the age of 30 and then a mammogram and MRI annually after that.
Cancer Network: Are there certain women for whom an MRI screening is specifically currently recommended?
Dr. McLaughlin: Yes. The American Cancer Society came out with specific MRI screening guidelines in 2007. These guidelines identify women based on high-quality evidence who should receive annual MRI screening; this includes women who are known BRCA mutation carriers but are unaffected, meaning they have never had breast cancer, and women who have a first-degree relative who is known to have a BRCA mutation but have not themselves been tested, as well as women with a lifetime risk greater than 20% to 25%. There is high-quality evidence suggesting that these women should have an annual mammogram and MRI. There is additionally good consensus-based evidence that suggests that women with other genetic mutations like PTEN deficiency and Cowden syndrome or p53 mutation and Li–Fraumeni syndrome should also receive an MRI annually in addition to mammography. Similarly to women with a first-degree relative with BRCA mutations, if you have a first-degree relative with one of these mutations but have not been tested, that is an indication that you should receive MRI screening. Another group of women included in the guideline recommendations are those who have a prior history of chest radiation before the age of 30. These women should have a mammogram and an MRI on an annual basis. There is another group-women with a lifetime risk of 15% to 20%-that should possibly be considered for MRI screening, but the American Cancer Society guidelines suggest that there is insufficient evidence.
Cancer Network: What is the difference between MRI screening and conventional mammogram? What does an MRI detect that perhaps mammography cannot?
Dr. McLaughlin: The way that the tests are done is totally different. A mammogram is more of an anatomical screen, looking at the breast tissue. It sees calcification very well and it has a very high specificity, which makes it a very good screening test. An MRI is both a functional and an anatomical test. Women who receive an MRI receive an injection of a gadolinium contrast dye, which gives imaging of the breast. The MRI images are not dependent on breast density, so that allows us to see the tissue in a different way, to evaluate blood flow and areas of increased blood flow, or enhancement, within the breast. This may show different activity based on what is going on in that area. These are images that mammograms don’t give us.
Cancer Network: You mentioned that these guidelines are based on high-quality evidence-are there any specific studies you can highlight that show that MRI screening enhances detection?
Dr. McLaughlin: There is not one specific study. There are about 10 or 11 prospective studies looking at the value of MRI screening. They demonstrate clearly that there is value in MRI screening in women who have a very high risk for breast cancer-those with significant family history or a BRCA mutation-because the sensitivity of MRI is much higher than that of mammography. These studies are prospective but not randomized, and they demonstrate benefit in finding additional cancers in this population.
Cancer Network: Are there any controversies associated with MRI screening?
Dr. McLaughlin: These days, the controversies are not so much in the group in which the guidelines support screening, but in this “insufficient evidence” group, which includes women with a lifetime risk of 15% to 20%, and those who have atypical hyperplasia, increased breast density, or a personal history of breast cancer. I think in this population of women, it’s a little bit more controversial about who should get an MRI and who should be screened with an MRI in their follow-up. Perhaps the controversy stems from the fact that most of the MRI screening guidelines rely on models that in large part incorporate and are heavily weighed based on family history of breast cancer, and in some of these situations there may be insufficient evidence. It may be that you have a high-risk lesion but not a family history of breast cancer. And if that is the case, then the current models in use and recommended by the guidelines don’t actually give you a good estimate of your true risk. In other words, there may be women in the ADH [atypical ductal hyperplasia], ALH [atypical lobular hyperplasia], LCIS [lobular carcinoma in situ], or breast density categories who would actually benefit from MRI because their lifetime risk is in fact greater than 15% to 20%. For example, there have been some good studies published in the New England Journal of Medicine that showed that women who have atypical hyperplasia lesions might have a lifetime risk of breast cancer between 25% and 30%, and this would certainly qualify them for MRI screening based on the lifetime risk calculations recommended by the American Cancer Society. So, I think the controversy really becomes, how do we define risk, what is the best model to use to evaluate patients, and how do we individualize this for patients, in order to optimize who is getting screening and at the same time minimizing the risk of multiple false-positive results, which would certainly happen if we screened everyone across the board.
Cancer Network: Currently in the United States, would you say that women, outside of this controversial group who should be getting screened, are receiving appropriate screening?
Dr. McLaughlin: I think so. I think the guidelines are pretty clear about the high-risk group and there is no doubt about those women. I think that in general we are definitely seeing an increase in the use of MRI itself and I think people are appropriately getting screened. There are other screening modalities out there that are gaining interest-different forms of mammography, tomosynthesis, molecular breast imaging, and those kinds of things. Right now we have no guidelines for those, and we have the most history, data, and consistent evidence supporting MRI.
Cancer Network: Thank you so much for joining us today, Dr. McLaughlin.
Dr. McLaughlin: No problem. Thank you so much for having me.