Prognosis classification of breast cancer with distant lymph node metastasis IIIc or M1 category

Background: In the American Joint Commission on Cancer (AJCC) staging manual, ipsilateral supraclavicular lymph node metastases (ISLM) were defined as N3c, while contralateral supraclavicular and subclavian lymph node, contralateral internal mammary lymph node, contralateral axillary lymph node, and cervical lymph node as distant lymph nodes metastasis (DLM) were classified as M1, stage IV. Herein, we used the information recorded in the Surveillance, Epidemiology, and End Results (SEER) database to compare patients' overall survival with DLM, ISLM, and distant organ metastasis. Methods: A total of 376 patients with ISLM, 562 patients with DLM, 5,069 patients with IIIc stage breast cancer, and 7,540 patients with distant organ metastasis from the SEER database (2004-2016) were included in the present study. R package was used to perform the Kaplan–Meier survival analysis among these four groups, and propensity score weighting (PSW) was used to minimize the differences in clinicopathological characteristics among groupsResults: After PSW, the median survival of ISLM, DLM, IIIc stage, and distant organ metastasis was 42 months, 50 months, 55 months, and 31months, respectively. DLM achieved significantly better overall survival than distant organ metastasis (pConclusion: The prognosis of breast cancer patients with DLM was similar to ISLM and IIIc stage, but much better than that of patients with distant organ metastasis. Also, combined-modality therapy significantly improved long-term survival. Consequently, it seems more reasonable to classify DLM as IIIc category instead of M1.