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. Data from patients with clinical T1–T2N0, human epidermal growth factor receptor 2‐positive breast cancer who either underwent upfront surgery or received neoadjuvant chemotherapy were extracted from two institutional databases. Nodal positivity rates were >20% at upfront surgery; neoadjuvant chemotherapy decreased nodal positivity rates, but axillary lymph node dissection rates were equivalent. [ABSTRACT FROM AUTHOR]