Surgery on Metastatic Foci is a Better Strategy for Stage IV Breast Cancer Patients with only Nonregional Lymph Node Metastasis

Introduction Our study aims to explore whether breast cancer patients with non-regional lymph node (NRLN) metastasis benefit from surgery on distant nodes, and to determine the influencing factors affecting the prognosis of this type of patient. Methods Information of invasive ductal carcinoma (IDC) patients from 2004 to 2016 was extracted from the Surveillance, Epidemiology, and End Results (SEER) database and analyzed by statistical methods, including multivariate Cox regression model, chi-squared test, propensity score matching (PSM), Kaplan–Meier plot, and log-rank test. Results A total of 4236 M1 patients met the designated criteria. Among 847 patients with only NRLN metastasis who have detailed information, only 114 patients received surgery on metastatic distant lymph nodes. The Kaplan–Meier plot for overall survival (OS) showed that the prognosis of NRLN metastatic patients was superior to visceral metastasis ( P < 0.0001) but similar to supraclavicular metastasis ( P = 0.33). In addition, NRLN metastatic patients who underwent surgery on the NRLNs were found to have superior prognoses in terms of both OS ( P = 0.041) and cancer-specific survival ( P = 0.034) compared with those who did not undergo NRLN surgery. We have also demonstrated that NRLN metastatic patients who have received radiotherapy plus chemotherapy for primary tumors gain superior survival compared with those who only received chemotherapy apart from NRLN surgery. Conclusion Surgery on NRLN and radiotherapy for the primary tumor improved the prognosis of NRLN metastatic patients. Thus, the classification of NRLN, especially contralateral axillary lymph node metastasis (CAM), into the M1 breast cancer stage should be reconsidered. Different locoregional treatment strategies for metastatic foci should be recommended for patients with only NRLN and patients with visceral metastasis.