Abstract PS4-11-02: Factors associated with lymph node metastasis and its prognostic impact in breast cancer patients with small tumors (≤2cm)

Abstract Introduction: Although previous randomized controlled trials have suggested that axillary surgery may be omitted in patients with clinically node-negative breast cancer with tumor ≤ 2cm (pT1), approximately 15% of these patients were found to have lymph node (LN) metastasis. Furthermore, while these studies demonstrated that axillary surgery, including sentinel LN biopsy, does not provide a therapeutic benefit, concern remain regarding the prognostic impact of occult LN metastasis. Therefore, the aim of our study was to identify factors associated with LN metastasis in small tumors (≤ 2cm) and to analyzed its impact on recurrence. Methods: We identified patients with pT1 primary breast cancer who underwent treatment at two hospitals between September 2003 and December 2019. To ensure accurate assessment of pathologic LN metastasis, patients who received neoadjuvant systemic therapy or did not undergo axillary surgery were excluded. Multivariate analysis was performed to identify factors associated with LN metastasis and to evaluate the impact of LN metastasis on recurrence-free survival (RFS). Results: A total of 1,745 patients were included in the study, of whom 384 (22.0%) had axillary LN metastasis. In the multivariate binary logistic regression model, LN metastasis was significantly more common in tumors larger than 1cm (odds ratio [OR], 2.94; 95% confidence intervals [CI], 0.15-4.08; P