Neoadjuvant chemotherapy (NACT) significantly impacts breast cancer management. After NACT, accurately determining the patient’s final axillary lymph node status (pathologic response, ypN0 vs. ypN+) is critical for surgical planning. A recent study specifically investigates how the primary tumor response on MRI Axillary Response can predict this outcome. This assessment aims to identify patients who may avoid the morbidity of extensive axillary surgery.
The retrospective study included 251 breast cancer patients. Overall, the probability of achieving a negative lymph node status (ypN0) was 60.2%. Importantly, the study calculated predictive metrics, reporting an overall Negative Predictive Value (NPV) of 79.2%. Subgroup analyses, stratified by clinical nodal (cN)-status and Oestrogen Receptor (ER) expression, revealed crucial differences in outcomes. The probability of ypN0 was substantially higher in cN0 patients (82%) compared to cN+ patients (39.5%). Likewise, ER-negative tumours showed a 78.2% ypN0 rate, versus 50.6% in ER-positive tumors.
MRI Axillary Response: Subgroup Findings
Breast Complete Response (BCR) on MRI proved highly significant in specific patient groups. In fact, the probability of finding residual disease (ypN+) despite a BCR on MRI was below 10% for cN0 patients and ER-negative tumours. Consequently, the study reported very high Negative Predictive Values (NPVs) for these two subgroups.
The NPV reached 92% in cN0 patients. Similarly, the NPV was 90.1% for ER-negative tumours. These high values suggest that a BCR on post-NACT MRI is an excellent tool to safely exclude ypN+ disease in these groups. However, the NPVs were lower in cN+ (62.2%) and ER-positive (72.2%) patients. Therefore, an MRI BCR is less reliable in these latter subgroups for safely excluding ypN+. This confirms that residual nodal disease remains a significant concern in these cohorts, even with a complete response observed on imaging.
Clinical Implications for Axillary De-escalation
Accurate, non-invasive methods to differentiate between patients with and without axillary pathologic complete response are currently lacking. Surgeons in India, for example, often perform extensive axillary clearance (Level III dissection) for locally advanced disease, even after a clinical complete response, due to historical concerns over false-negative rates. This practice carries a risk of significant lymphedema and morbidity. Moreover, current international guidelines are moving towards de-escalating axillary surgery for patients with confirmed pCR.
This study provides strong evidence supporting the use of post-NACT breast MRI as a key component in risk stratification. Ultimately, if a cN0 or ER-negative patient achieves BCR on MRI, the surgeon can confidently consider less invasive options, such as Sentinel Lymph Node Biopsy (SLNB). In contrast, for cN+ and ER-positive patients, a higher index of suspicion for residual disease remains crucial, regardless of the MRI response. Consequently, routine pathologic assessment of the nodes is still warranted in these higher-risk groups. Furthermore, other studies indicate that MRI accuracy is better for tumours like triple-negative, which aligns with the ER-negative finding here.
Frequently Asked Questions
Q1: What is a Breast Complete Response (BCR) on MRI?
A BCR on MRI is defined as no residual evidence of a discrete mass or suspicious enhancement in the primary breast tumour after neoadjuvant chemotherapy (NACT) is completed. It signifies a promising response to treatment.
Q2: Why is the Negative Predictive Value (NPV) important for surgical planning?
The NPV is the probability that a patient truly does not have the disease (ypN0) when the test result (BCR on MRI) is negative. A high NPV (e.g., >90%) means the test is excellent at ruling out residual cancer in the lymph nodes, allowing surgeons to safely consider less aggressive surgery.
Q3: Which breast cancer subgroups can use post-NACT MRI most effectively to guide axillary surgery?
Post-NACT MRI is most effective for guiding de-escalation of axillary surgery in patients who were clinically node-negative at baseline (cN0) or who have Estrogen Receptor (ER)-negative tumours, due to the high NPV observed in these groups. The probability of residual lymph node disease (ypN+) is below 10% in these cohorts if a Breast Complete Response is achieved on MRI.
References
- van Amstel FJG et al. Primary tumour response on breast MRI as a predictor of axillary pathologic response in breast cancer patients treated with neoadjuvant chemotherapy. Eur Radiol. 2025 Dec 23. doi: 10.1007/s00330-025-12249-x. PMID: 41436643.
- Sadeghi-Naini M, et al. MRI and Prediction of Pathologic Complete Response in the Breast and Axilla After Neoadjuvant Chemotherapy for Breast Cancer. Ann Surg Oncol. 2017 Sep;24(9):2540-2547.
- Chaudhary V, et al. Correlation of Pathologic and Radiologic Complete Response in the Axilla after Neoadjuvant Chemotherapy for Breast Cancer. Clin Med Int Libr. 2018;2:033.
- Hagerty J, et al. Correlation of pathologic and radiologic complete response in the axilla after neoadjuvant chemotherapy for breast cancer. J Clin Oncol. 2018 May 20;36(15_suppl):e12089-e12089.
- Yoo D, et al. Predicting Axillary Response to Neoadjuvant Chemotherapy: Breast MRI and US in Patients with Node-Positive Breast Cancer. Radiology. 2020 Jan;294(1):50-58.
- Sharma M, et al. Role of MRI in evaluation of residual tumor burden following neoadjuvant therapy in patients with breast cancer. Indian J Radiol Imaging. 2025 Jan 15;35(1):73.
- Kakarala M, et al. Axillary Staging after Neoadjuvant Chemotherapy in Breast Cancer. ArrangoizMD. Published online April 15, 2025.
- Prabhudesai SR, et al. Level III dissection in locally advanced breast cancer following neoadjuvant chemotherapy: a retrospective study. NIH. Published online December 2024.