The use of preoperative magnetic resonance imaging (MRI) did not significantly reduce positive margins after breast-conserving surgery, according to data presented during a press briefing at the 2023 American Society of Breast Surgeons Annual Meeting.1 Although MRI has been shown to detect additional disease in some women with breast cancer, findings from the SHAVE and SHAVE2 trials showed that MRI imaging was not associated with clear tumor margins. Conversely, patient age and tumor size were found to be critical factors in predicting margin status.
“MRI exams are costly and potentially stressful for patients,” said study author Marissa Howard-McNatt, MD, FACS, FSSO, Professor of Surgery, Director Breast Care Center, Wake Forest Baptist Health. “The thought is that they will help physicians achieve negative margins during the initial surgery. However, our study shows this is not the case.”
No one wants to take a patient back to the operating room. Advances in surgical techniques and technology ... may prove successful in adding precision to breast cancer surgery.— Marissa Howard-McNatt, MD, FACS, FSSO
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Breast-conserving surgery has been a mainstay in breast cancer management, with safe and reliable outcomes compared with mastectomy when tumor-free margins are obtained. However, breast-conserving surgery may be associated with a higher rate of positive margins, ranging up to 27% in the literature.2
“Reexcision surgery can contribute to greater morbidity, patient anxiety, poor cosmetic outcome, and health-care system overload,” Dr. Howard-McNatt explained. “Given the desire to reduce reoperations, much attention has been paid to using preoperative imaging to assess the extent of disease to mitigate this risk.”
MRI has been shown to detect additional disease in 16% of women with breast cancer, Dr. Howard-McNatt noted. However, MRI is also associated with a higher positive rate, ranging up to 12%.
Study Methods: SHAVE Trials
The SHAVE and SHAVE2 trials were prospective randomized trials involving more than 10 institutions. Study participants included female patients with stage 0 to 3 breast cancer who underwent breast-conserving surgery; all patients signed an informed consent prior to participation. Patients were randomly assigned intraoperatively to have either resection of cavity shaved margins or lumpectomy without additional margins being taken. Intraoperative pathologic assessment of margins was not performed. The preoperative use of MRI was at the discretion of the treating surgeon.
Patient Age and Tumor Size
Between 2011 and 2018, 631 patients with breast cancer (stage 0 to 3) were enrolled in these two prospective trials. Median patient age was 64, and the median tumor size was 1.3 cm. Of these patients, 165 had palpable tumors, 7% had invasive lobular histology, 33% had an extensive intraductal component, and 7% had been treated with neoadjuvant chemotherapy.
As Dr. Howard-McNatt reported, MRI was performed in 193 patients perioperatively, with 31.1% of these patients later found to have positive margins. Among patients who did not receive an MRI, 38.8% had positive margins. Although patients who had an MRI performed were less likely to have a positive margin than those who did not, this did not reach statistical significance, said Dr. Howard-McNatt.
On multivariate analysis, controlling for patient age, race, ethnicity, receipt of neoadjuvant chemotherapy, histologic subtype, receptor status, and tumor size, MRI was not significant in predicting margin status. However, patient age and tumor size were the only two factors that remained independently associated with margin status in the model and were statistically significant.
“Perhaps surprisingly, we did find that tumor size was predictive of margin status,” Dr. Howard-McNatt commented. “However, this may be attributable to an inaccurate initial assessment of the extent of the actual tumor size for a variety of reasons. For example, tumors may be discontinuous or have satellite lesions that may touch the edge of a specimen.”
Despite the lack of benefit in reducing positive margins and reoperations, Dr. Howard-McNatt noted that MRI remains a valuable tool in many other preoperative breast cancer applications, including evaluation of patients with lobular breast cancer, known genetic mutations, and extremely dense breasts. Shaving of the tumor cavity—removing additional tissue around the initial tumor cavity during a first operation—often has been shown to be effective in eliminating a second surgery, she said.
“No one wants to take a patient back to the operating room,” Dr. Howard-McNatt continued. “Advances in surgical techniques and technology, including new imaging modalities such as contrast-enhanced mammography, may prove successful in adding precision to breast cancer surgery.”
Expert Point of View
Julie A. Margenthaler, MD, FACS, Professor of Surgery at Washington University School of Medicine, St. Louis, told The ASCO Post that breast magnetic resonance imaging (MRI) in patients with a new diagnosis of breast cancer remains controversial with respect to surgical planning benefit. As Dr. Margenthaler explained, prior studies clearly showed that MRI can detect multicentric and/or contralateral disease in a group of patients that does ultimately alter the care for those patients.
“Whether MRI impacts the assessment of the extent of disease to a degree that alters surgical outcomes is not well established,” said Dr. Margenthaler. “The current study supports the notion that MRI does not alter the surgical margin positivity rates for patients undergoing breast conservation.”
“However, I would caution that this study may not be generalizable to other populations, given that MRI was not randomized in either of these trials, and the margin positivity rates were significantly higher than what has been reported in more contemporary studies,” she noted. “As a result, I would continue to support a careful evaluation of selective MRI use in each surgeon’s practice.”
DISCLOSURE: Dr. Howard-McNatt reported no conflicts of interest. Dr. Margenthaler reported no conflicts of interest.
1. Cairns A, Howard-McNatt M, Namm J, et al: Does preoperative MRI reduce positive margins after breast conserving surgery? 2023 American Society of Breast Surgeons Annual Meeting. Abstract. Presented April 19, 2023.
2. Thompson JL, Wright GP: The role of breast MRI in newly diagnosed breast cancer: An evidence-based review. Am J Surg 221:525-528, 2021.