The American Joint Committee on Cancer Prognostic Staging System for Breast Cancer: Sustained Relevance of Anatomic Criteria on 5-Year Survival.

PURPOSE: In 2018, the American Joint Committee on Cancer (AJCC) revised the TNM staging system for breast cancer (BC), incorporating biological factors into anatomical staging. This study evaluated the clinical impact of this integration and the relative prognostic contribution of anatomical and biological factors to 5-year overall survival (OS). METHODS: A retrospective analysis was conducted on a cohort of 1075 patients diagnosed with BC at the Breast Centre of São João University Hospital (2015-2020), using clinicopathological data from a EUSOMA-certified database. The primary endpoint was 5-year OS and was analyzed using Kaplan-Meier estimates, log-rank tests, and Cox proportional hazards regression. RESULTS: Stage migration occurred in 42.1% of patients when switching from anatomical to pathological prognostic staging, with 37.5% downstaging. Downstaging was observed across all stages and molecular subtypes except triple-negative BC (TNBC). Consistent with previous studies, 5-year OS rates were equivalent between staging systems, with no significant survival differences between patients who remained in a stage and those who migrated to it. On multivariable analysis, tumor size showed the strongest prognostic impact on 5-year OS, particularly for T3/T4 disease, while N3 status remained independently associated with poorer outcomes. Histological grade and molecular subtype showed more limited prognostic significance; only TNBC was independently associated with worse prognosis. CONCLUSION: The AJCC pathological prognostic staging system promotes substantial stage migration while refining survival prediction. Nevertheless, anatomical tumor burden remains the predominant determinant of 5-year OS, reinforcing the continued clinical relevance of traditional TNM staging despite the incorporation of tissue-based biomarkers.