Clinical significance of HER2-positive and triple-negative status in small (≤ 1 cm) node-negative breast cancer.

Background: Data regarding the clinical significance of HER2(+) and TN status in patients with small node-negative tumors are limited and conflicting. It remains unclear who, among those with small lesions, might benefit from more aggressive adjuvant therapy.

Methods: We identified all node-negative breast cancer patients with tumor size ≤ 1 cm diagnosed between January 1, 1995 and December 31, 2008 using our institutional breast service database. Patients were classified according to their receptor status into 3 groups: (1) hormone receptor (HR)-positive (estrogen receptor [ER]- or progesterone receptor [PR]-positive, HER2(-)); (2) HER2(+) (immunohistochemistry 3(+) or fluorescence in situ hybridization amplification ≥ 2); and (3) TN (ER(-), PR(-), and HER2(-)). RFS was calculated using Kaplan-Meier methods.

Results: Among 656 patients with tumors ≤ 1 cm, 494 (75%) of the patients were HR(+), 107 (16%) were HER2(+), and 55 (9%) were TN. Median age was 59 years (range, 27-92 years). Median follow-up was 3.5 years. The 5-year RFS rates were 98.2%, 97.1%, and 83.5% in patients with HR(+), HER2(+), and TN tumors, respectively (P < .001). In multivariate analysis, TN status was associated with worse RFS (hazard ratio, 6.70; 95% confidence interval [CI], 3.02-14.86), and HER2(+) was not (hazard ratio, 1.64; 95% CI, 0.73-3.69).

Conclusions: TN, but not HER2(+) status, was associated with worse RFS in patients with T1abN0 tumors, and adjuvant chemotherapy might be considered in patients with TN breast cancer.