Yes: MRI should be considered in the preoperative setting for specific clinical indications.
MRI, like any technology, has its strengths and weaknesses, with high sensitivity but low specificity. Importantly, MRI provides excellent soft tissue contrast with anatomic 3-D detail, and is not impeded by high breast density.
Admittedly, MRI only incrementally increases cancer detection rates in either the ipsilateral or contralateral breasts of all patients, and when used in the preoperative setting does not affect short-term surgical outcomes for all patients. Therefore, MRI should not be used for routine screening or routine preoperative screening.
That said, there are specific clinical situations where preoperative MRI may provide surgeons with valuable information. These include patients who have:
• Invasive lobular carcinoma.
• Neoadjuvant chemotherapy.
• Occult primaries in extremely dense breasts.
Invasive lobular carcinomas are more likely to be multi-centric, multi-focal, and/or bilateral than other breast cancer types, and they are more difficult to diagnose because they infiltrate into tissue, making it extremely difficult to determine the extent of disease. In this setting, MRI can more accurately determine tumor size than mammography. Mammography underestimates the tumor size significantly more frequently than does MRI. In addition, among women with this cancer subtype, MRI can significantly reduce the rate of excision ( Breast Cancer Res Treat. 2010;119;415-22 ).
We know that women at risk for systemic recurrence will not be cured with surgery alone. Neoadjuvant therapies give us the opportunity to refine local therapy options, better understand the patient’s response to therapy and prognosis, and accelerate targeted drug development to improve outcomes. To accomplish all of these goals, we need a noninvasive way to assess tumors before, during, and after neoadjuvant treatment. MRI is unsurpassed for evaluating the extent of tumors, showing in larger tumors, for example, the complexity of tumor and stroma.
MRI is also a biomarker for response to therapy and has been shown to be an independent predictor of event-free survival. In addition, MRI is more accurate than either clinical exam, mammography, or ultrasound for determining residual tumor size following neoadjuvant chemotherapy ( Radiology. 2012;263:663-72 ).
Lastly, for patients with an occult primary (by imaging) breast cancer or primary presentation of axillary node involvement, MRI has been found to have an approximately 90% sensitivity for identifying a primary tumor, and a 95% accuracy at locating the tumor in patients who undergo surgical excision. Mammography cannot distinguish a tumor mass that is dense relative to surrounding tissue. However, MRI can distinguish a tumor which is obscured by dense breast tissue because tumors are visualized on MRI by rapid contrast uptake and washout.
MRI is a catalyst for change, but you have to use it and all technology wisely: At the time of diagnosis for select patients, for screening only those patients with very breast dense tissue and very high risk for developing breast cancer, and, perhaps most importantly, for postcancer surveillance only in women at very high risk of recurrence where standard tools such as mammography are expected to have lower performance (for example, very dense breast tissue). Overuse of MRI will increase false positives, anxiety, and cost. However, used appropriately, MRI can be used to help usher in a change in practice through the evaluation of response to neoadjuvant therapy and novel therapeutic approaches to both invasive and in situ lesions.
With improvements in technology and techniques such as diffusion-weighted imaging, the value of MRI in the preoperative setting can only continue to grow. We can also expect greater performance for presurgical staging with more refined technologies for breast imaging, localization, and biopsy, but the costs have to come down. Breast-dedicated MRI technologies may address this need.
Laura Esserman, MD, is a professor of surgery and radiology at the University of California, San Francisco, and Director of the Carol Franc Buck Breast Care Center at the UCSF Mount Zion campus.
No: MRI leads to unnecessary surgeries and does not improve short-term surgical outcomes.
The key word in this debate is “routinely.” I agree that preoperative MRI may have a role in about 5% of all cases – namely in women with occult primaries and those who undergo neoadjuvant chemotherapy. But for the vast majority of patients, the 95%, I would argue that preoperative MRI has the potential to do more harm than good.
Thirty years of experience providing breast conserving therapies without MRI has taught us several important lessons:
• Selection of patients for breast-conserving therapy is not a big problem.
• The incidences of local recurrence and contralateral breast cancers have decreased over time, antedating the use of MRI.
• Surgical excision of all microscopic subclinical disease is not necessary to achieve good long-term outcomes.
In National Surgical Adjuvant Breast and Bowel Project studies from the 1990s, in the era before the use of aromatase inhibitors or HER-2 blockade, the 10-year incidence of ipsilateral breast tumor recurrence ranged from 3.5% to 6.5% in the breast cancer population at large.
In addition, the incidence of contralateral breast cancers has been declining at a rate of approximately 3% per year, thanks to the use of adjuvant systemic therapies.
We have known since the 1960s, thanks to our colleagues in pathology, that somewhere between 30% and 60% of breast cancers that appear to be localized have microscopic subclinical disease which is treated with breast irradiation. More recently, we have recognized that we can leave behind cancer in the axilla in anywhere from 13% to 27% of patients who are not receiving direct axillary radiation, and see failure rates of 1% or less.
In the context, then, of our current understanding of breast cancer biology, what outcomes could MRI be expected to improve, since the purpose of a test is to improve patient outcomes?
We know that MRI will not improve survival, because 30 years ago randomized trials showed us that survival was equal between breast conservation and mastectomy.
MRI has no apparent effect on reducing local recurrences either, as shown in an analysis of data on 3,180 patients published in 2014 ( J Clin Oncol. 2014;32:292 ).
Regarding contralateral breast cancer, a 2007 study ( N Engl J Med. 2007;356:1295-303 ) showed that among 969 women, MRI found unsuspected cancer in the contralateral breast within 1 year of diagnosis in 3.1%, a finding used to support the argument that all women with breast cancer should have an MRI. But a second study using Surveillance, Epidemiology and End Results (SEER) data on 339,790 women with 2.5 million person-years of follow-up found that the 10-year rate of contralateral cancers was 2%-3% of women with estrogen-receptor–positive tumors, and in 5%-6% of those with estrogen-receptor–negative tumors, strongly suggesting that MRI leads to detection and treatment of disease that would never become clinically evident.
Finally, I would point to evidence that MRI does not improve short-term surgical outcomes, as shown in a meta-analysis my colleagues and I conducted of two randomized controlled trials and seven cohort studies, involving a total of 3,112 patients ( Ann Surg. 2013;257:249-55 ).
We found that after adjustment for age, having an MRI was associated with a three-fold greater chance of having a mastectomy, and MRI did not significantly reduce either the need for re-excision or unexpected conversion to mastectomy. We also performed a subanalysis of infiltrating lobular cancers, and found that there was no statistically significant benefit for MRI in these patients.
The overall rate of mastectomy was 25.5% among patients who had an MRI, vs. 18.2% for those who did not.
So to summarize: MRI finds two to three times more cancer than observed rates of local recurrence, leading to unnecessary mastectomies and does not improve short-term surgical outcomes, and there is no evidence indicating that MRI decreases local recurrence.
Monica Morrow, MD, FACS, is chief of the breast service in the department of surgery and holds the Anne Burnett Windfohr Chair of Clinical Oncology at Memorial Sloan Kettering Cancer Center in New York.