Nodal positivity and systemic therapy among patients with clinical T1-T2N0 human epidermal growth factor receptor-positive breast cancer: Results from two international cohorts.

BACKGROUND: The optimal treatment strategy for patients with small human epidermal growth factor receptor 2 (HER2)-positive tumors is based on nodal status. The authors' objective was to evaluate pathologic nodal disease (pathologic lymph node-positive [pN-positive] and pathologic lymph node-positive after preoperative systemic therapy [ypN-positive]) rates in patients who had clinical T1-T2 (cT1-cT2)N0M0, HER2-positive breast cancer treated with upfront surgery or neoadjuvant chemotherapy (NAC). METHODS: Two databases were queried for patients who had cT1-cT2N0M0, HER2-positive breast cancer: (1) the Dana-Farber Brigham Cancer Center (DF/BCC) from February 2015 to October 2020 and (2) the Hospital Clinic of Barcelona and the Hospital Clinico of Valencia (HCB/HCV) from January 2012 to September 2021. The pN-positive/ypN-positive and axillary lymph node dissection (ALND) rates were compared between patients who underwent upfront surgery versus those who received NAC. RESULTS: Among 579 patients from the DF/BCC database, 368 underwent upfront surgery, and 211 received NAC; the rates of nodal positivity were 19.8% and 12.8%, respectively (p = .021). The pN-positive rates increased by tumor size (p < .001), reaching 25% for those with cT1c tumors. The ypN-positive rates did not correlate with tumor size. NAC was associated with decreased nodal positivity (odds ratio, 0.411; 95% confidence interval, 0.202-0.838), but the ALND rates were similar (22 of 368 patients [6.0%] who underwent upfront surgery vs. 18 of 211 patients [8.5%] who received NAC; p = .173). Among 292 patients from the HCB/HCV database, 119 underwent upfront surgery, and 173 received NAC; the rates of nodal positivity were 21% and 10.4%, respectively (p = .012). The pN-positive rates increased with tumor size (p = .011). The ALND rates were equivalent by treatment strategy (23 of 119 patients [19.3%] who underwent upfront surgery vs. 24 of 173 patients [13.9%] who received NAC; p = .213). CONCLUSIONS: Among patients who had cT1-cT2N0M0, HER2-positive breast cancer, approximately 20% who underwent upfront surgery were pN-positive, and the rate reached 25% for those with cT1c tumors. Given the opportunity for tailored therapy among lymph node-positive, HER2-positive patients, these data provide rationale for future analyses investigating the utility of routine axillary imaging in patients with HER2-positive breast cancer.