Rates of local regional recurrence were very low for patients with early-stage triple-negative and HER2-positive breast cancer regardless of whether or not they received a breast MRI for staging and surgical planning, according to findings from the phase III Alliance A011104/ACRIN 6694 trial presented at the 2025 San Antonio Breast Cancer Symposium (SABCS; Abstract GS2-07).
"Preoperative breast MRI did not improve any of the oncologic outcomes that we measured: local regional recurrence, distance recurrence–free survival, or overall survival," said lead study investigator Isabelle Bedrosian, MD, Surgical Oncologist and Professor of Breast Surgical Oncology at The University of Texas MD Anderson Cancer Center, during a press briefing at SABCS. "A011104 adds to the body of evidence that preoperative breast MRI for staging patients with newly diagnosed breast cancer does not result in improved oncologic outcomes or in improvement in surgical care. The routine use of breast MRI for staging disease does not appear to be warranted."
Background and Study Methods
Breast MRI is widely used for local staging and surgical planning for patients with newly diagnosed breast cancer, as it can detect disease not seen by mammography. However, it was previously unknown if breast MRI truly leads to improved patient outcomes. "The clinical question that we set about to address in this trial was whether the identification and subsequent surgical resection of MRI-detected disease reduced the rate of local recurrence," Dr. Bedrosian said.
A total of 319 patients with newly diagnosed clinical stage I to II, triple-negative or estrogen and progesterone receptor–negative/HER2-positive breast cancer who were eligible for breast-conserving surgery were enrolled in the study. Dr. Bedrosian explained that these patients are known to have the highest risk of recurrence. Patients with multifocal tumors that could be resected in a single operation were also eligible for enrollment, but patients who were carriers of germline BRCA1/2 mutations, those with bilateral breast cancer, and patients with a prior history of breast cancer were all excluded. All enrolled patients were randomly assigned to undergo staging breast MRI or not. Patients assigned to the MRI arm had to undergo an MRI scan within 30 days of the mammogram.
Key Findings
Of the enrolled patients, 93.4% underwent surgical intervention, with 91.9% undergoing breast-conserving surgery. No significant differences were observed between the two groups (91.9% with MRI vs 92.7% without; P = .62). Dr. Bedrosian pointed out that although presurgical ultrasound was not a necessary inclusion criteria but rather an institutional preference, the vast majority of patients underwent breast ultrasound prior to surgery.
Eighty-five percent of patients received chemotherapy, with 17.6% receiving neoadjuvant chemotherapy (an amendment to eligibility criteria); among these patients who received neoadjuvant chemotherapy, the overall pathologic complete response rate was 39.3%, the rate in the no-MRI arm was 52% vs 29% in the MRI arm (P = .10).
Rates of adjuvant radiation were comparable between the two arms (85.4% in the no-MRI arm and 85% in the MRI arm).
A total of 298 patients were evaluable for local regional recurrence at a median of 61.1 months of follow-up, and no differences were reported in local regional recurrence rates between the arms. The rate of 5-year local regional control was 93.2% (95% confidence interval [CI] = 89.0%–97.6%) in the MRI group and 95.7% (95% CI = 92.3%–99.1%) in the no-MRI group (hazard ratio [HR] = 1.1; 95% CI = 0.3–3.9). Subgroup exploratory analyses did not show any significant benefit for the use of presurgical breast MRI.
"The rate of local regional recurrence overall is quite low. It is actually lower than what we have anticipated when we were designing the study," Dr. Bedrosian said.
At 5 years, the distant recurrence–free rate for the entire study population was 94.3% (95% CI = 91.7%–97.1%) and the 5-year overall survival rate was 92.2% (95% CI = 89.1%–95.4%), and no differences were reported between the groups.
"So how to think about these negative results: There could be a couple of possible explanations for why we saw no benefit for the use of preoperative breast MRI. It is possible in the setting of chemotherapy and radiation therapy, resecting MRI-detected disease may not be necessary, that these are adequately treated with these other modalities of care that patients are already receiving. Alternatively, it is also possible that the advances in mammographic imaging that we have seen over the last 10 to 15 years, as well as the widespread use of ultrasound that we detected in our trial may have limited the utility of MRI for local staging. We have analyses ongoing to try to distinguish between these two possibilities."
Dr. Bedrosian also noted that breast MRIs have also been used to reduce the likelihood of positive margins and re-operation, and said that the study is also exploring that context.
Disclosure: The study was supported by the National Cancer Institute of the National Institutes of Health. Dr. Bedrosian reported no conflicts of interest. For full disclosures of the other study authors, visit abstractsonline.com.
