Number of negative lymph nodes as a prognostic factor for ypN0-N1 breast cancer patients undergoing neoadjuvant chemotherapy.

Some of node-positive patients could have a pathologically complete response in terms of lymph nodes. For these patients, the number of negative lymph nodes (NLNs) may be higher than that in the same-stage patients who initially received mastectomy. After neoadjuvant chemotherapy (NAC), the following treatment especially the postmastectomy radiotherapy (PMRT) is controversial for ypN1 (with one to three positive lymph nodes after NAC) patients. A total of 289 patients who received NAC from 2006 to 2009 were included in the investigation. The prognostic value of the number of NLNs on these patients was analyzed. Besides, we analyzed if the number of NLNs would give some indications on PMRT in ypN1 patients. The follow-up of all the patients began the first chemotherapy on 15 March 2015. The 5-year disease-free survival (DFS) and overall survival (OS) rates were determined as 67.2 and 81.1 %, respectively. The number of NLNs was associated with primary stage (p < 0.001), pathological tumor size (p < 0.05), pathological nodal stage (p < 0.001), and pathological stage after NAC (p < 0.001). The univariate and multivariate analyses revealed that the number of NLNs is an independent prognostic factor in both DFS and OS. In ypN0-N1 stage, patients with >13 NLNs had better DFS (p < 0.001) and OS (p < 0.001) than the patients with ≤13 NLNs. Although the fact patients in ypN2-N3 stage with >13 NLNs had better DFS and OS than the others, there were no significant statistical difference. In the subgroup analysis, PMRT improved the OS (p < 0.05) and DFS (p < 0.05) of ypN1 patients with ≤13 NLNs. The number of NLNs is a prognostic indicator in ypN0-N1 patients. Patients in ypN1 stage with less number of NLNs will benefit from PMRT.