Prognostic Impact of Residual T and N Status After Neoadjuvant Therapy in Breast Cancer

Residual disease after neoadjuvant systemic therapy (NST) is strongly associated with prognosis in breast cancer. However, currently available indices such as the Residual Cancer Burden (RCB) and Neo-Bioscore are complex and not readily applicable in daily clinical practice. This study aimed to evaluate the prognostic significance of residual tumor morphology using only pathological T and N factors as a simple and clinically implementable index.

Among 327 patients who received NST at our institution, 174 non-pathological complete response (non-pCR) cases who underwent axillary lymph node dissection were analyzed. Patients were classified according to the presence or absence of residual T and/or N factors (ypT+/ypN+, ypT+/ypN-, ypT-/ypN+). Disease-free survival (DFS) and cancer-specific survival (CSS) were assessed using Kaplan-Meier and Cox regression analyses.

Patients who achieved pCR had significantly better DFS and CSS (p<0.001 and p=0.010, log-rank) than those with residual disease. Among the non-pCR cohort, the ypT+/ypN+ group showed markedly worse DFS and CSS (p= 0.010 and p<0.001, log-rank) than patients without simultaneous residual T and N positivity. Multivariate analysis confirmed that concurrent ypT and ypN positivity was an independent predictor of poor DFS (hazard ratio=0.33; 95% confidence interval=0.17-0.62; p<0.001), along with high Ki67 expression.

Residual T and N positivity after NST represents a simple yet powerful prognostic indicator in breast cancer. This two-factor classification, easily derived from routine pathology, may serve as a practical reference for post-NST risk stratification and inform decisions regarding additional adjuvant treatment.