Development and validation of a nomogram incorporating YpT stage for predicting ypN0 using multicenter data in clinically node-positive breast cancer.

Recent studies have demonstrated that breast pathological complete response (pCR) can be accurately diagnosed preoperatively using image-guided needle biopsy after neoadjuvant chemotherapy (NAC), underscoring the value of incorporating ypT stage into prediction models for axillary response (ypN0). Based on this evidence, we developed and externally validated a nomogram to predict ypN0 in patients with clinically node-positive (cN+) breast cancer treated with NAC. This retrospective, multicenter study included 609 patients with cN + breast cancer who underwent NAC followed by surgery. A nomogram was developed using a training cohort (n = 330) and validated in an independent cohort (n = 279). Diagnostic performance was evaluated using the area under the receiver operating characteristic curve (AUC), calibration plots, decision curve analysis (DCA), and positive predictive value (PPV). The nomogram incorporated five predictors: ypT stage, cN stage, hormone receptor status, HER2 status, and post-NAC cN stage. It showed strong discriminative ability, with bias-corrected AUCs of 0.858 in the training cohort and 0.855 in the validation cohort. Calibration and DCA confirmed good model performance. PPV exceeded 0.90 when the nomogram-predicted probability was ≥ 0.7 in both cohorts. This nomogram demonstrated high diagnostic accuracy for predicting ypN0 and may support the selection of candidates for axillary surgery de-escalation based on post-NAC biopsy findings. Prospective validation using biopsy-confirmed pCR is warranted.