Prognosis of patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative, 1–3 node-positive breast cancer meeting the high-risk criteria of the monarchE trial: a comparison between macrometastasis and micrometastasis

BACKGROUND: The monarchE trial enrolled patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, node-positive, high-risk early breast cancer (EBC). Although both macrometastasis and micrometastasis were eligible, the number of patients with only micrometastasis was not reported, leaving their prognosis uncertain. This study compared outcomes of patients with 1-3 positive axillary lymph nodes (pALNs), including those with only micrometastases and those with macrometastases, according to monarchE high-risk criteria. METHODS: We retrospectively reviewed 844 patients with HR-positive/HER2-negative/node-positive EBC from a prospectively maintained institutional database and classified them into four groups: Group 1, 1-3 pALNs (including macrometastasis) with grade 3 tumors or tumors ≥ 5 cm; Group 2, 1-3 pALNs (only micrometastasis) with grade 3 tumors or tumors ≥ 5 cm; Group 3, 1-3 pALNs (including macrometastasis) with grade < 3 tumors and tumors < 5 cm; and Group 4, 1-3 pALNs (only micrometastasis) with grade < 3 tumors and tumors < 5 cm. Invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS) were analyzed using the Kaplan-Meier method and log-rank test. Univariable Cox models assessed associations between clinical factors and outcomes. RESULTS: Group 2 showed outcomes comparable to Group 1 (5-year IDFS: 80.7% vs. 83.7%; DRFS: 89.5% vs. 87.9%). In univariate analysis, only tumor size-rather than Group 2 or histological grade-was prognostic for IDFS and DRFS. Sensitivity analyses restricted to patients undergoing axillary lymph node dissection yielded consistent results. CONCLUSIONS: Among HR-positive/HER2-negative EBC, high-risk patients with only micrometastasis demonstrated prognoses similar to those with macrometastasis.