23 December 2025
OPBC-07/microNAC study: Less axillary surgery after chemotherapy - except in triple-negative breast cancer
After neoadjuvant chemotherapy (NAC), many breast cancer patients can avoid extensive axillary surgery, provided the regional lymphatic pathways are consistently treated with regional nodal irradiation (RNI). Axillary recurrences remain rare overall – however, there is one important exception: in triple-negative breast cancer, the risk of axillary recurrence increases substantially if axillary lymph node dissection (ALND) is omitted.
In personalised breast cancer therapy, an increasingly important question after neoadjuvant chemotherapy (NAC) is how radical axillary management needs to be. The international OPBC-07/microNAC study, led by Prof Walter P. Weber, shows that among patients with residual micrometastases (ypN1mi), axillary recurrences are uncommon overall—and remain low even without axillary lymph node dissection (ALND), provided regional nodal irradiation (RNI) is delivered consistently. A key exception is the triple-negative subtype, in which axillary recurrence risk rises significantly when ALND is omitted. The study results were published on 22 December 2025 in the renowned journal The Lancet Oncology.
Evidence from 30 countries: direct implications for clinical practice
The analysis included 1585 patients from 84 centres in 30 countries. Around half underwent ALND, and approximately 80% received RNI. The overall 3-year axillary recurrence rate was around 2% and did not differ meaningfully between patients who had ALND and those in whom ALND was omitted. Independently of this, omission of RNI was associated with an increased risk of axillary recurrence. Rates of invasive recurrence (locoregional or distant) were similarly frequent in both groups. For triple-negative breast cancer, axillary recurrence was higher without ALND (8.7% without ALND vs 2.4% with ALND).
"Our results show that many patients can avoid major axillary surgery if the lymphatic pathways are treated with targeted radiotherapy. In triple-negative breast cancer, we are more cautious—here, surgery may still be appropriate."
Prof. Walter P. Weber, head of the study, medical head of the department and chief physician of breast surgery at the University Hospital Basel
Axillary strategies after neoadjuvant chemotherapy (NAC) in the presence of micrometastases
A project within the OPBC network
Principal Investigator
Prof. Walter P. Weber, Chief of Breast Surgery, Head of the Department of Breast, Abdomen and Pelvis, University Hospital Basel
Study design
International, multicentre, retrospective cohort study
Study centres
84 centres in 30 countries (2013-2023)
Patients
1,585 patients with micrometastases (ypN1mi) after NAC
Follow-up
Median 3.1 years
DKF Scientific Services
Consulting, project management, regulatory affairs
Original publication
Oncological outcomes with and without axillary lymph node dissection in patients with residual micrometastases after neoadjuvant chemotherapy (OPBC-07/microNAC): an international, retrospective cohort study, Montagna G, et al., The Lancet Oncology, Volume 27, Issue 1, 2026, Pages 57-67, ISSN 1470-2045, https://doi.org/10.1016/S1470-2045(25)00598-4.
More information
Oncoplastic Breast Consortium (OPBC)
TAXIS-Studie on clinicaltrials.gov
Nodal Burden and Oncologic Outcomes in Patients With Residual Isolated Tumor Cells After Neoadjuvant Chemotherapy (ypN0i+): The OPBC-05/ICARO Study. Montagna G, et al., J Clin Oncol. 2025 Mar;43(7):810-820. doi: 10.1200/JCO.24.01052. Epub 2024 Nov 7. PMID: 39509672; PMCID: PMC11856002.
Omission of Axillary Dissection Following Nodal Downstaging With Neoadjuvant Chemotherapy. Montagna G, et al., JAMA Oncol. 2024 Jun 1;10(6):793-798. doi: 10.1001/jamaoncol.2024.0578. PMID: 38662396; PMCID: PMC11046400.