This study evaluated whether human epidermal growth factor receptor 2 status is an independent, poor prognostic marker in patients with small (≤1 cm), node-negative breast cancer and whether a subgroup of patients with these small tumors who might benefit from adjuvant systemic therapy could be identified.
Long-term outcomes and hence the role of adjuvant therapy in patients with small (≤1 cm), node-negative breast cancer remain unclear. This study's objective was to evaluate whether human epidermal growth factor receptor (HER)-2 status is an independent, poor prognostic marker in patients with these tumors and to identify a subgroup of patients with these small tumors who might benefit from adjuvant systemic therapy. All patients with a diagnosis of a node-negative breast tumor measuring ≤1 cm and available HER-2 test results between January 1, 2001, and December 31, 2005, at the three Mayo Clinic sites were identified. Clinicopathologic data were compared in three groups: HER-2−, HER-2+, and triple-negative (TN) tumors. Of the 421 tumors identified, 364 (86.5%) were HER-2−, 28 (6.7%) were HER-2+, and 29 (6.9%) were TN. The median follow-up time was 1,015 days (range, 1–2,549 days). Groups were balanced in terms of patient age and tumor histology. Eleven patients with HER-2− tumors (3.0%), seven with HER-2+ tumors (25.0%), and eight with TN tumors (27.6%) received adjuvant chemotherapy. Follow-up data were available for 357, 28, and 28 patients in the three groups, respectively. Death rates in the three groups were 6.4% (23 of 357) (one recurrence-related death), 0% (0 of 28), and 7.1% (2 of 28) (one recurrence-related death), respectively. During follow-up, the tumor recurred in nine patients: four were HER-2− tumors (1.1%), two were HER-2+ tumors (7.1%), and three were TN tumors (10.7%). Patients with small, node-negative breast tumors have an excellent prognosis, but HER-2+ and TN tumors appear to have a higher recurrence rate, warranting consideration for broad use and optimization of systemic adjuvant treatments.