SAN ANTONIO – Patients with stage 1 or 2, hormone receptor (HR)-negative breast cancer had similar five-year rates of locoregional recurrence whether or not they underwent preoperative breast magnetic resonance imaging (MRI) in addition to diagnostic mammography to determine the extent of their cancer, according to results from the phase III Alliance A011104/ACRIN 6694 clinical trial presented at the San Antonio Breast Cancer Symposium (SABCS), held December 9-12, 2025.
Breast MRI is commonly included as part of the diagnostic workup of breast cancer due to its ability to detect disease that may not be found by mammography, explained Isabelle Bedrosian, MD , lead investigator of the study and a surgical oncologist and professor of breast surgical oncology at The University of Texas MD Anderson Cancer Center.
She noted, however, that including MRI often leads to additional testing, delays in surgery, and increases the patient's financial burden. "These costs and delays could be justified if there were demonstrable improvement in patient outcomes associated with the use of MRI, but its impact on oncologic outcomes has been understudied," Bedrosian said.
"For years, the underlying assumption has been that detecting additional disease by MRI, so that it can be surgically removed, was an important way to reduce the risk of disease recurrence," she added. "We designed the clinical trial to test that assumption, setting out to determine whether detecting and removing areas of disease not detected by mammography translated to improved long-term outcomes."
The trial enrolled 319 patients with newly diagnosed stage 1 or 2, HR-negative breast cancer who were eligible for lumpectomy and who did not have germline BRCA1/2 mutations, bilateral breast cancer, or a history of prior breast cancer. Bedrosian noted that the study enrolled patients with HR-negative breast cancers due to their higher risk of disease recurrence compared with those with HR-positive breast cancers.
All patients had undergone diagnostic mammography with or without ultrasound prior to trial enrollment. Upon enrollment, patients were randomly assigned to undergo additional imaging by breast MRI (MRI arm) or to receive no further imaging (no MRI arm). The proportion of women undergoing lumpectomy and receiving adjuvant radiation was similar between arms.
After a median follow-up of 61.1 months, 93.2% of the 161 patients in the MRI arm and 95.7% of the 158 patients in the no MRI arm remained free of locoregional recurrence, a difference that was not statistically different.
"The rate of locoregional recurrence was quite low in both arms of the trial, and the inclusion of MRI did not lower it any further," Bedrosian said.
Breast MRI also did not significantly impact the rates of five-year distant recurrence-free survival (94.2% in the MRI arm vs. 94.4% in the no MRI arm) nor overall survival (92.9% with MRI vs. 91.4% without MRI).
In a subset of 56 patients who received neoadjuvant chemotherapy, pathologic complete response rates were numerically lower in the MRI arm (36% vs. 52%), but the difference was not statistically significant. Bedrosian noted that these data should be considered preliminary due to the very small sample size of this subgroup.
"Our trial results show that there is no improvement in the oncologic outcomes of patients who undergo preoperative breast MRI staging as compared with those who do not," Bedrosian summarized. She added that the results build on data from the COMICE clinical trial, which demonstrated that breast MRI did not reduce the rates of subsequent surgery .
"Our results further imply that there is no clinical utility to using preoperative MRI for the diagnostic workup of breast cancer patients to guide surgical treatment," Bedrosian said. "We conclude that the routine use of MRI in this context is not warranted."
Bedrosian explained that the lack of benefit associated with preoperative breast MRI could be because it did not detect many additional lesions beyond mammography in this population and/or because identifying and removing these additional lesions had minimal impact on the rate of disease recurrence.
"I think it is likely a combination of both reasons," she noted, adding that ongoing analyses are examining how often breast MRI identified additional lesions in the trial population to better understand why breast MRI did not impact oncologic outcomes.
A limitation of the study was that 93.4% of patients had clinically node-negative breast cancer at baseline. Bedrosian explained that the high proportion of node-negative disease could partly account for the low rates of locoregional recurrence observed in both arms, but she noted that it is unlikely to explain the finding that locoregional recurrence rates were similar whether or not patients underwent breast MRI.
Another limitation identified by Bedrosian was that the trial population skewed older, with a mean age of 58.9 years at study enrollment. The benefit of MRI is thought to be greater in patients under the age of 50, due to their typically denser breast tissue that can limit the sensitivity of mammography. However, an analysis of participants who were under age 50 suggested that this subgroup similarly may not benefit from MRI, according to Bedrosian.
The study was supported by the National Cancer Institute of the National Institutes of Health. Bedrosian declares no conflicts of interest.
