Axillary staging in post-neoadjuvant chemotherapy breast cancer patients: prognostic analysis and validation of axillary nodal metrics and comparison of the pathological node staging versus the lymph node ratio systems in a 169-case series.

[BACKGROUND] Neoadjuvant chemotherapy (NAC) is considered disruptive for axillary nodal staging in breast cancer patients, by altering the total number of excised nodes, and the number of positive and negative nodes. We aimed to identify the axillary variable having the strongest association with survival, and also to compare the prognostic efficacy of the pathological node (pN) staging versus the lymph node ratio (LNR) systems in post-NAC cases.

[METHODS] In this retrospective single-center study of 169 post-neoadjuvant chemotherapy breast cancer patients, three absolute axillary nodal counts (positive [], negative [], and total excised nodes []) and six derived ratios (, , , , , and ) were evaluated. Associations with survival and relative prognostic strength were assessed using univariate, bivariate, and multivariate Cox regression models. The prognostic performance of pathological node (pN)-staging and lymph node ratio (LNR) systems was evaluated using Kaplan–Meier survival analysis.

[RESULTS] The , , and and values had no significant associations with survival, while the value had the strongest association with survival ( < 0.0001). The ranking of axillary variables based on their strength of association with survival was:  >  (or ) >  (or ). Both the pN-staging and LNR systems and also their respective bases (the and values) were significantly associated with survival (respectively:  = 0.005,  = 0.041,  < 0.0001,  = 0.006).

[CONCLUSION] Both the pN- and LNR staging systems can significantly classify post-NAC patients into survival groups, while the pN-staging system showed superior credentials to identify high-risk cases.

[TRIAL REGISTRATION] Not applicable, as this is a retrospective observational study and not a clinical trial.