Increasing rates of axillary pathologic complete response (axillary pCR) after neoadjuvant chemotherapy (NACT) challenge the routine use of axillary surgery. The investigated strategy uses an on-treatment core needle biopsy (CNB) of the primary breast tumor, performed during NACT, to detect early tumor eradication in the breast and to predict nodal response. The study assessed whether absence of residual disease on on-treatment CNB defines an "early responder" population that correlates with axillary pCR and favorable survival, potentially supporting axillary surgery de-escalation.
This was a prospective cohort of patients treated between 2013 and 2021 who underwent an on-treatment CNB of the primary tumor after 2–4 cycles of NACT. Early responders were defined as those with no residual disease on on-treatment CNB. The primary comparisons were between on-treatment CNB status and final axillary pathological outcomes; survival endpoints included overall survival (OS) and event-free survival (EFS). The article reports aggregate results for 1,693 patients in the study cohort.
Across the full cohort of 1,693 patients the overall axillary pCR rate was 54.3%. Within the subset of 500 patients classified as early responders by on-treatment CNB, 83.4% achieved axillary pCR on final pathology. These findings indicate a strong association between absence of residual disease on on-treatment CNB and subsequent axillary sterilization after completion of NACT.
When stratified by clinical nodal status, early responders showed different predictive values. In clinically node-negative (cN0) patients who were early responders, 98.0% (99/101) had no nodal disease at surgery, indicating that on-treatment CNB negativity in cN0 patients closely predicts absence of axillary metastasis.
In clinically node-positive (cN+) early responders, 79.7% achieved axillary pCR. The predictive performance improved when on-treatment CNB results were combined with radiologic assessment: when early-response CNB negativity was concordant with a post-treatment MRI complete response, the axillary pCR rate rose to 89.6% overall in that combined group. Reported subgroup values for the combined CNB-plus-MRI approach included 92.6% axillary pCR in cN1 patients and 90.0% in cN2 patients.
These data suggest that combining pathologic assessment from on-treatment CNB with imaging response (MRI) can increase the probability of correctly identifying patients who will have axillary pCR after NACT, particularly among those who were node-positive at presentation.
Survival analysis reported superior five-year overall and event-free survival among early responders with hormone receptor–negative (HR-negative) tumors, with statistical significance indicated by p < 0.001. The source reports that early responders demonstrated better long-term outcomes in this biologic subgroup, linking early on-treatment CNB response to favorable prognosis in HR-negative disease.
The study authors conclude that on-treatment CNB can reliably identify patients likely to achieve axillary pCR and therefore offers an approach to guide axillary surgery de-escalation. For cN0 patients with on-treatment CNB negativity, the very high rate of absent nodal disease suggests potential for omission or minimization of axillary surgical staging in selected cases. For cN+ patients, combining on-treatment CNB with post-treatment MRI to confirm complete response may better select individuals with a high probability of axillary pCR who could be considered for more conservative axillary management.
The findings support use of an early pathologic assessment during NACT as part of response-adapted strategies and underline the potential to tailor systemic and surgical treatment based on early tumor biology and response.
The article states that original contributions are included in the article and supplementary material. The previewed source provides key cohort-level outcomes and subgroup rates but does not report procedural details such as CNB technique specifics, sampling protocols, per-patient characteristics beyond nodal status categories, or complication rates related to CNB. Detailed patient selection criteria, full multivariable analyses, and granular survival curves are included in the full article and supplementary files referenced by the publication but were not reported in the previewed content.
Overall, the prospective data presented support on-treatment CNB as a promising tool to identify early responders during NACT and to inform response-adapted axillary surgery de-escalation strategies.