Journal of the National Cancer Institute Advance Access originally published online on July 29, 2008
JNCI Journal of the National Cancer Institute 2008 100(15):1052-1054; doi:10.1093/jnci/djn284
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© Oxford University Press 2008.
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Possible MRI–Mastectomy Link Sparks Debate on MRI's Role in Breast Cancer Management
After years of decline, the number of breast cancer patients choosing mastectomy over breast-conserving surgery is on the rise, and a new study suggests that the use of highly sensitive magnetic resonance imaging (MRI) may be at least partly responsible.
The study raises questions about the appropriate use of MRI in making treatment decisions about breast cancer and whether the technology should be offered to early-stage, low-risk breast cancer patients.
"Sometimes our technologies get ahead of our evidence-based medicine," said Matthew Goetz, M.D., a medical oncologist at the Mayo Clinic and lead investigator of the study, which looked at surgical outcomes of all early-stage breast cancer patients seen at Mayo Clinic's Rochester, Minn., hospital from 1997 to 2006. In the retrospective study, presented at the American Society for Clinical Oncology meeting in May, the research team found an association between mastectomy rates and preoperative MRI. The researchers controlled for age, cancer stage at diagnosis, and other confounding variables.
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Among breast cancer patients at the Mayo Clinic, mastectomy rates declined from 47% in 1997 to 30% in 2003, when only 11% of women received an MRI. By 2006, MRI use had doubled to 22% and the number of women having a mastectomy had returned to its mid-1990s level. The study is the first large retrospective study to find a possible association between mastectomy rates and use of MRI over several years, and it supports what many doctors have noted anecdotally in their own practices.
Goetz said that he and his colleagues undertook the study in response to a general sense that more women were undergoing mastectomy in recent years, after yearly declines in the late 1990s. Goetz attributed those declines to a series of studies culminating in a 1990 National Institutes of Health consensus statement that concluded that women with early-stage breast cancer survive as well with breast-conserving surgery and adjuvant radiation as with mastectomy. At the same time, patient advocacy groups lobbied legislators to ensure that surgeons inform breast cancer patients about their surgical options, and laws requiring full disclosure of surgical options were enacted in many states, pressuring doctors to reduce mastectomy rates (JNCI 1994;86:1202–8).
However in recent years, breast cancer surgeons have begun using imaging techniques such as ultrasound and MRI to assist in surgical planning. Although the Mayo study did not include information on whether MRI influenced women's decisions for or against having a mastectomy, the study highlights a potentially serious problem associated with increasing use of routine MRI. This technique creates a meticulous image of soft tissue that can help diagnose breast cancers missed by mammography and ultrasound imaging, but it is also associated with a false-positive rate of 70%–80%. By contrast, the false-positive rate for screening mammography is about 10%. Other conditions, such as fibroadenomas and fibrocystic changes, can masquerade as cancer in an MRI image. Because of the technique's low specificity, patients end up requiring further imaging or biopsies for lesions that are probably not cancer.
"I wonder whether patients reach a threshold where they are unwilling to deal with the uncertainty of future imaging and biopsies," Goetz said. "They are tired of a physician saying, ‘We're not sure, follow up in 6 months with a repeat test,’ and so those patients may say, ‘Thank you very much, but let's just proceed with a mastectomy.’"
Surgeons are seeing suspicious lesions with MRI that were not visible before, and once those lesions come to light they demand some kind of action, said Richard Bleicher, M.D., a surgical oncologist at Fox Chase Cancer Center in Philadelphia and lead author of a recent review of the use of MRI in breast cancer management. "But to say that we should be doing MRI in these patients to find the 10%–30% of women who have foci that we didn't know about before sort of flies in the face of the fact that we were equally successful with breast conservation before we knew about them."
From his review, which appeared in the November 2007 issue of Oncology, Bleicher concluded that MRI does not have a proven benefit for routine selection of breast conservation. Because the rate of local recurrence of breast cancer is already low, he said, the benefit of routine MRI use does not outweigh the risk of unnecessary additional surgery. To show that many breast cancers detected by MRI may never have become clinically relevant, Bleicher compared the 5-year rate of breast cancer incidence reported in the SEER (Surveillance, Epidemiology, and End Results) registry with the 1-year incidence rate reported by Constance Lehman, M.D., Ph.D., and her colleagues in a New England Journal of Medicine study of the use of MRI in newly diagnosed breast cancer patients.
"An abnormal MRI in a woman with cancer often leads the physician or the patient to automatically assume that it is additional disease and they may automatically go to mastectomy without actually obtaining a biopsy [specimen] of these other areas to prove whether or not they represent disease," said Tari King, M.D., a breast cancer surgeon at Memorial Sloan-Kettering Cancer Center, New York. "We are seeing that a lot."
"To date there is no clinical evidence that finding additional sites of occult disease with preoperative MRI affects patient outcome," she said. "If we do an MRI in everyone with breast cancer, we will identify additional sites of occult disease in 3%–5% of patients. If we then change treatment plans on the basis of these findings, we most certainly are going to be doing more mastectomies, but the long-term follow-up data from breast conservation trials suggest that local recurrence rates are already low and continue to improve in more recent decades. Therefore, we are lacking the clinical data to suggest that doing more mastectomies is going to benefit patients."
Doctors are split in their assessment of the value of MRI, and even those who have espoused its use are rethinking the effect of additional imaging studies on patients in the absence of proven benefit.
Breast surgeon Kevin Bethke, M.D., an assistant professor of surgery at Northwestern University Feinberg School of Medicine, recently published a small retrospective study of his own practice over a 1-year period beginning in April 2005. During the study, 155 of 242 women with breast cancer received a preoperative MRI of both breasts. Half of the women who received MRI had at least one additional suspicious lesion that required further testing. The MRI results changed the surgical management plan in 23% of patients, 10 of whom were upgraded from a lumpectomy to a mastectomy and 21 of whom required a more extensive lumpectomy. Overall, the study found a false-positive rate of 80%. Two patients declined a biopsy on a suspicious MRI finding and chose to have a mastectomy. Bethke concluded in the May 2007 Archives of Surgery report that that 10 women must undergo a breast MRI for one to have a beneficial change in experience but that nonetheless MRI does have a place in evaluation of newly diagnosed patients. However, in a recent interview he said that he is now less inclined to use MRI after seeing its effects on patient anxiety. "Patients are frustrated with the low specificity of MRI and the fact that it often leads to more testing, usually a biopsy for a suspicious area," he said. "If I have a choice, I choose bilateral ultrasound over MRI simply because it has a lower rate of false positives. The trouble with MRI is we are now seeing lesions that we couldn't see before, and once you see it you can't ignore it."
But he added that there are some cases in which MRI clearly has a place, such as lobular carcinoma, multifocal disease, and "occult" cases in which no lesion is visible by mammography.
Breast cancer surgeon Stephen Grobmyer, M.D., of the University of Florida College of Medicine in Gainesville believes that at his institution MRI helped in selecting patients for breast conservation. He and his colleagues reported in the May issue of the Journal of the American College of Surgeons that MRI was useful in surgical planning and reducing the need for a second surgery in patients who had breast-conserving cancer therapy. In all, the outcome of 79 patients evaluated between January 2005 and July 2007 showed that 10% of patients required a second surgery when they were evaluated with MRI compared with a rate of 20% reported from the same hospital a few years earlier.
"We think it is helping us better select patients for breast conservation, and in some cases, design a better operation for patients at the time of partial mastectomy," Grobmyer said. "In modern surgical series, the rate of reexcision has been reported between 20% and 50%. We think MRI is better at local staging. [But] with a retrospective study, we can't prove that."
Grobmyer pointed out that for patients considering partial breast irradiation, in which radiation exposure is limited, MRI may prove useful in ensuring that no small areas of disease are being missed. In the past, whole-breast radiation may have been "covering up" small areas of disease that were present, he suggested.
The trouble, Goetz said, is that "there are absolutely no guidelines in how to use MRI in a preoperative setting [in breast cancer]. What our data demonstrate is that there will certainly need to be future guidelines that are established." Until then, patient decisions are likely to continue to be made out of fear of the worst, he added.
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