Twenty-five Years Overall Survival Prognostic Value of the Lymph Node Ratio in De Novo Metastatic Breast Cancer

Abstract

Background/aim: The lymph node ratio (LNR) indicates the number of involved lymph nodes divided by the number of lymph nodes found during axillary exploration. This study investigated the prognostic value of the LNR in de novo metastatic breast cancer (dnMBC). We hypothesized that LNR might predict long-term survival even in cases where the disease has already disseminated beyond the regional stage.

Patients and methods: Patients with dnMBC were selected from the Surveillance, Epidemiology, and End Results (SEER) 9-registries database 1988-2012. Positive lymph nodes (npos) were categorized as pN0 (npos=0), pN1 (npos=1 to 3), pN2 (npos=4 to 9), and pN3 (npos≥10). The LNR was categorized as Lnr0 (LNR=0), Lnr1 (LNR=0.01 to 0.20), Lnr2 (LNR=0.21 to 0.65), and Lnr3 (LNR≥0.65). The prognostic values were compared using Gini's mean difference Δ of the restricted mean overall survival time (RMST) according to npos versus LNR groups.

Results: A total of 12,085 patients with dnMBC had LNR data. At 25 years follow-up, the npos RMSTs were 10.4, 5.1, 5.8, and 5.0 years, for pN0 to pN3, respectively. The npos Gini's Δ was 2.8 years (standard error ±0.2). The LNR RMSTs were 10.4, 9.9, 7.6, and 4.0 years for Lnr0 to Lnr3, respectively. Δ for LNR was 3.6 (±0.2) years. Among node positive cases, the LNR low-risk group had an RMST of 9.9 years, approaching node-negative cases, while the high-risk group had an RMST of 4.0 years.

Conclusion: LNR identified different prognostic groups, suggesting a possible role of lymph node involvement as a marker of lymphangiogenesis or lymphatic changes in the immune microenvironment, which warrants further investigation in dnMBC.

Keywords: Gini’s mean difference; dispersion; measure of separation; prognostic classifiers; restricted mean survival time.