Do T1a breast cancers profit from adjuvant systemic therapy? A multicenter retrospective cohort study of 325 T1a-patients

Small tumor size (≤5 mm, T1a) carries an excellent prognosis. Controversy exists over the extent of the variety of treatment approaches. We therefore explored the effect of adjuvant systemic therapy (AST) on recurrence free survival (RFS) and overall survival (OAS) for the group of T1a-tumors. Methods The multicenter study population included 9625 early breast cancer patients, diagnosed between 1992 and 2008. 5196 patients were T1 (54.0 %) and 325 of these patients (3.4 %) were T1a. Results Compared to patients with AST RFS and OAS were significantly worse for patients who did not receive AST (RFS: p = 0.001; OAS: p = 0.021). Even N0-T1a-patients ( n = 279) significantly profited from AST (RFS: p = 0.001; OAS: p = 0.006). Patients with at least one poor prognostic factor (HR−, HER2+, N1 or G3) without AST also showed a significantly worse outcome (RFS: p = 0.026; OAS: p = 0.024) compared to pT1a-patients with AST. Consensus guidelines state that the prognosis of patients with T1a that are N0 is uncertain even if HER2 is amplified or overexpressed. In our study nodal-negative (N0) T1a-patients ( n = 279) without AST showed a significantly worse RFS ( p = 0.001), and a significantly worse OAS ( p = 0.006) compared to those patients with AST. In multivariate analysis even after adjusting by age, grading, hormonal receptor status, HER2/neu-status and nodal status T1a-patients without AST were associated with a significantly worse RFS resp. OAS compared to patient with AST (RFS: p = 0.002; OAS: p = 0.007). Conclusions There is an association between AST and improved RFS or OAS for breast cancer patients with T1a tumors.