Objectives: In breast cancer, large tumor size, positive nodal stage and a triple-negative tumor subtype are associated with reduced survival, but the interactions between these prognostic factors are not well understood.
Material and methods: Here we re-evaluated the impact of tumor size, nodal stage and tumor subtype on disease-free survival (DFS), overall survival (OS), distant disease-free survival (DDFS) and breast cancer specific survival (BCSS) in a retrospective analysis using data from the adjuvant SUCCESS A trial. Subgroup analyses were conducted to assess whether the effect of tumor size and nodal stage on survival depended on tumor subtype.
Results: Increasing tumor size, higher nodal stage and triple negative breast cancer (TNBC) were associated with unfavorable prognosis (all p < 0.001). There was no significant interaction between tumor subtype and tumor size (p > 0.5 for all four survival endpoints), but we found significant interactions between tumor subtype and nodal stage (p < 0.05 for all four survival endpoints), with no differences in survival among tumor subtypes for patients with pN0 tumors (all p > 0.05) and pronounced differences in survival among tumor subtypes for patients with positive nodal stage (all p < 0.001).
Conclusions: This analysis confirms tumor size, nodal stage and tumor subtype as independent prognostic factors in high-risk early breast cancer. Nodal-positive patients with TNBC had a considerably worse outcome compared to nodal-positive patients with another tumor subtype. This underlines the importance for early detection particularly for patients with TNBC.
Trial registration: EudraCT 2005-000490-21; ClinicalTrials.gov Identifier: NCT02181101.
Keywords: High-risk breast cancer; Interaction effects; Molecular subtype; Nodal stage; Prognostic factors; Tumor size.
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