To explore the risk factors of level Ⅲ axillary lymph node (ALN) metastasis in breast cancer patients received neoadjuvant chemotherapy and analyze their significance on patient prognosis.

A total of 306 breast cancer patients with ALN metastasis in Southwest Hospital, Army Medical University from January 2007 to December 2014 were enrolled for a retrospective study. All the patients underwent neoadjuvant chemotherapy of two or more cycles, followed by mastectomy and ALN dissection (levelⅠ-Ⅲ). χ² test was used to analyze the relationship between clinicopathological characteristics of patients and level Ⅲ ALN metastasis, and Logistic regression model was used to analyze the independent risk factors for level Ⅲ ALN metastasis. Kaplan-Meier survival curve and Log-rank test were used for survival analysis.

Univariate analysis showed that stage cT, stage cN, clinical stage, the number of metastatic level Ⅰ-Ⅱ ALNs and efficacy of neoadjuvant chemotherapy were correlated with the status of level Ⅲ ALNs (χ²=24.116, 65.139, 83.175, 140.223, 41.482, all P<0.001). Multivariate Logistic regression analysis showed that after neoadjuvant chemotherapy, the patients with stage Ⅲ_A, Ⅲ_B or Ⅲ_C breast cancer had significantly higher risk of level Ⅲ ALN metastasis compared with stage Ⅱ_A breast cancer (Ⅲ_A vs Ⅱ_A: OR=29.095, 95%CI: 2.596-326.034, P=0.006; Ⅲ_B vs Ⅱ_A: OR =75.145, 95%CI: 5.083-1 110.837, P=0.002; Ⅲ_C vs Ⅱ_A: OR=124.097, 95%CI: 10.082-1 527.514, P<0.001). The risk of level Ⅲ ALN metastasis was significantly higher in patients with ≥4 metastatic level Ⅰ-Ⅱ ALNs than in patients with < 4 metastatic ALNs (OR=21.813, 95%CI: 9.633-49.389, P<0.001). The patients with stable or progressive disease had significantly higher risk of level Ⅲ ALN metastasis compared with the patients with clinical complete response (OR= 17.138, 95%CI: 2.894-101.481, P=0.002). All patients were followed up for median 78 months (range: 7-147 months). The patients with level Ⅲ ALN metastasis after neoadjuvant chemotherapy had significantly lower 5-year DFS and OS compared with those with level Ⅰ-Ⅱ ALN metastasis (DFS: 35.1% vs 78.9%, P<0.001; OS: 52.8% vs 83.9%, P<0.001).

Patients with clinic stage Ⅲ_A or over breast cancer are in high risk of level Ⅲ ALN metastasis after neoadjuvant chemotherapy. The patients with more than 4 metastatic ALNs at level Ⅰ-Ⅱ after neoadjuvant chemotherapy may present residual lymph node metastasis if no dissection level Ⅲ ALNs is performed during surgery. The status of level Ⅲ ALNs is an important prognostic factor in breast cancer patients.