Predictive factors of pathologically node-negative disease for HER2 positive and triple-negative breast cancer after neoadjuvant therapy.

Background: With the improvement of the efficacy of neoadjuvant therapy (NAT) that is guided by molecular subtypes, the rate of pathologically node-negative disease after NAT (ypN0) is increasing for HER2 positive (HER2+) and triple-negative (TN) breast cancer patients. The necessity of axillary surgery for patients with high ypN0 has been questioned. This study aimed to identify patients among HER2+ and TN breast cancer with low risk for axillary metastases after NAT, and, perhaps, they are suitable for selective elimination of axillary surgery staging.

Methods: From January 2010 to August 2018, 865 breast cancer patients who underwent NAT were included in this retrospective clinical study, and 184 patients (21.3%,184/865) suffered from TN and HER2+ breast cancer and received full-course NAT. The correlation among clinicopathological characteristics of HER2+ and TN breast cancer and ypN0 were analyzed.

Results: Among the 184 HER2+ and TN breast cancer patients, tumor staging, lymph node staging and Ki-67 before NAT, clinically node-negative disease after NAT (ycN0), and breast radiologic and pathologic complete response (bpCR) were correlated with ypN0 (P<0.05). Lymph node staging before NAT (OR =0.363, P<0.001), ycN0 (OR =4.995, P<0.001) and bpCR (OR =11.285, P<0.001) were the independent effects of ypN0. The ypN0 rate after NAT in cN0/1 patients with bpCR and ycN0 (97.6%, 40/41) was significantly higher than that in cN2/3 patients (62.5%, 10/16) (P<0.001). Among the 37 patients with initial nodal ultrasonography showing cN0 disease, 17 of 17 (100.0%) with and 18 of 20 (90.0%) without bpCR had no evidence of residual nodal disease (P=0.178). Among the 42 patients with cN1 to ycN0, 23 of 24 (95.8%) with and 10 of 18 (55.6%) without bpCR had no evidence of residual nodal disease (P<0.001). Patients without bpCR had a relative risk for nodal residual metastases of 10.560 (95% CI: 2.720-41.003; P<0.001) compared with those with bpCR in cN1 group.

Conclusions: In terms of HER2+ and TN breast cancer patients, clinical lymph node staging before NAT, ycN0 and bpCR were the independent predictors of ypN0. bpCR was highly correlated with nodal status after NAT. The risk of axillary lymph nodes residual metastases after NAT in the patients of bpCR with cN0 and cN1 to ycN0 was less than 5%, thus making it possible to selectively avoid axillary surgery.