Axillary Pathologic Complete Response as a Stronger Prognostic Marker than Breast pCR in Clinically Node-Positive Stage II-III Breast Cancer.

BACKGROUND

Pathologic complete response (pCR) after neoadjuvant systemic therapy (NAST) predicts improved survival in breast cancer, but the relative prognostic value of breast versus axillary pCR in initially node-positive disease remains unclear.

METHODS

We analyzed 455 patients with clinically node-positive stage II-III breast cancer treated with NAST (2010-2022). Patients were classified by breast-axilla response patterns: both-site pCR (n = 99), breast-only pCR (n = 24), axilla-only pCR (n = 117), and neither pCR (n = 215). The primary endpoint was invasive disease-free survival (IDFS); overall survival (OS) was secondary. Multivariable Cox models assessed prognostic associations adjusted for clinicopathologic covariates.

RESULTS

Median follow-up was 57.2 months; 135 IDFS events, and 118 deaths occurred. In head-to-head analysis, axillary pCR showed numerically stronger prognostic associations than breast pCR (IDFS adjusted hazard ratio [aHR] 0.441 vs. 0.501; OS aHR 0.373 vs. 0.544). Compared with neither pCR, both-site pCR (IDFS aHR 0.217, 95% confidence interval [CI] 0.12-0.394) and pooled discordant response patterns achieving one-site pCR (aHR 0.464, 95% CI 0.304-0.709) demonstrated favorable outcomes, whereas breast-only pCR, observed in small, underpowered subgroup (n = 24), did not show a statistically significant benefit (aHR 0.928, P = 0.849). Five-year IDFS was 89% (both-site pCR), 77% (axilla-only pCR), 65% (breast-only pCR), and 63% (neither pCR). Findings remained robust in sensitivity analyses restricted to biopsy-confirmed node-positive patients and ALND-only subsets.

CONCLUSIONS

In clinically node-positive breast cancer treated with NAST, axillary pCR showed numerically stronger prognostic associations than breast pCR, although this apparent difference should be interpreted cautiously. Post-neoadjuvant nodal status may help to refine risk stratification and inform adjuvant treatment planning.