Outcomes in patients with small node-negative invasive breast cancer

Purpose There is controversy whether systemic therapy is warranted in patients with small node-negative tumors, especially among those with HER2(+) and triple negative breast cancers (TNBC). In this study we sought to compare survival and recurrence rates (RR) in patients with T1mi,a,bN0M0 breast cancer by tumor type. Methods Review of a prospectively maintained data base between January 1, 2000 through December 31, 2013 identified 71 patients with HER2(+) tumors, 545 with hormone receptor (HR)(+)/HER2(-) tumors, and 45 with TNBC. The three groups were compared with respect to RR, disease-free survival (DFS), and overall survival (OS). Patients with HER2(+) disease and TNBC who received chemotherapy were compared to those who did not. Results At mean follow-up of 4.9 years, the 5-year OS was 95% and 5-year DFS was 98%. RR for HER2(+), HR+/HER2(-), and TNBC was 7.0%, 3.7%, and 4.4% respectively (P = 0.2). There was no significant difference in OS (P = 0.9) and DFS (P = 0.4) amongst the three groups. On multivariable analysis, use of adjuvant chemotherapy was not associated with improvement in DFS or OS. When patients with HER2(+) breast cancer and TNBC who received chemotherapy were compared to those who did not, there was no difference in death rates (P = 0.3). Conclusions Patients with T1mi,a,bN0M0 invasive breast cancer have an excellent prognosis. The three molecular subtypes differed significantly in age, tumor size, and tumor grade, but had similar RR, DFS, and OS. Chemotherapy was not associated with improved survival. Tumor subtype may not influence recurrence and survival in such small early stage tumors.