Abstract: Background and purpose: Neoadjuvant chemotherapy (NAC) has become the standard treatment mode for locally advanced breast cancer patients. This study aimed to explore the feasibility of selective elimination of axillary surgery staging after NAC in human epidermal growth factor receptor 2 (HER2) positive and triple-negative breast cancer (TNBC) patients, and to assess which patients would acquire greater benefits from it. Methods: From Jan. 2010 to Aug. 2018, 865 patients who underwent surgery after NAC in Shandong Cancer Hospital and Institute were included in this retrospective study to analyze the correlation between clinicopathological characteristics of HER2 positive and TNBC patients and pathologically negative axillary lymph nodes after NAC (ypN ₀ ). Results: Among the 184 (21.3%) HER2 positive and TNBC patients receiving NAC, tumor staging, lymph node staging and Ki-67 before NAC, clinically node-negative (ycN ₀ ), breast radiologic complete response (brCR) and breast pathologic complete response (bpCR) after NAC were correlated with ypN ₀ (P<0.05). Clinical lymph node staging before NAC (OR=0.363, P<0.001), bpCR (OR=11.285, P<0.001) and ycN ₀ (OR=4.995, P<0.001) were the independent predictors of ypN ₀ . Among 37 patients with clinically nodal-negative breast cancer before (cN ₀ ) and after (ycN ₀ ) NAC, 17 of 17 (100.0%) with and 18 of 20 (90.0%) without a bpCR had no evidence of residual nodal disease (P=0.178). Among 42 patients with cN ₁ to ycN ₀ , 23 of 24 (95.8%) with and 10 of 18 (55.6%) without a bpCR had no evidence of residual nodal disease (P<0.001). Patients without a bpCR had a relative risk for nodal residual metastases of 10.56 (95% CI: 2.720-41.003; P<0.001) compared with those with a bpCR in cN ₁ group. Conclusion: In HER2 positive and TNBC patients, bpCR is highly correlated with nodal status after NAC. The risk of axillary lymph nodes residual metastases after NAC in the patients of bpCR with cN ₀ and cN ₁ to ycN ₀ was less than 5%, making it possible to selectively eliminate axillary surgery staging.

Key words: Breast cancer, Neoadjuvant chemotherapy, Triple-negative breast cancer, Human epidermal growth factor receptor 2 positive, Axillary surgery staging