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

[BACKGROUND/AIM] 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.

[PATIENTS AND METHODS] 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.

[RESULTS] Patients who achieved pCR had significantly better DFS and CSS (<0.001 and =0.010, log-rank) than those with residual disease. Among the non-pCR cohort, the ypT+/ypN+ group showed markedly worse DFS and CSS (= 0.010 and <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; <0.001), along with high Ki67 expression.

[CONCLUSION] 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.