Circulating STREM-1 as a biomarker of myeloid-driven inflammation in breast cancer: Diagnostic and prognostic significance

Background: Circulating biomarkers that reflect tumor-associated immune-inflammatory activation may help refine breast cancer assessment. Triggering receptor expressed on myeloid cells-1 (TREM-1) amplifies myeloid-driven inflammatory signaling, and its soluble form (sTREM-1) can be measured in serum. However, the diagnostic and prognostic relevance of pretreatment circulating sTREM-1 in breast cancer remains insufficiently defined. Methods: This single-center retrospective observational study included 132 treatment-naive patients with stage I-III breast cancer, 68 patients with benign breast disease, and 60 healthy controls. Serum sTREM-1, conventional tumor markers, C-reactive protein (CRP), and derived inflammatory indices, including NLR, PLR, LMR, and SII, were analyzed. Associations with clinicopathological features, diagnostic performance, and disease-free survival (DFS) were evaluated using correlation analysis, receiver operating characteristic (ROC) curves, Kaplan-Meier analysis, and Cox regression models. Results: Serum sTREM-1 was significantly elevated in breast cancer compared with benign disease and healthy controls (P < 0.001). Higher sTREM-1 levels were associated with larger tumor size, lymph node involvement, advanced stage, high histological grade, and elevated Ki-67 expression (all P < 0.05). sTREM-1 correlated positively with CRP NLR, PLR, and SII and negatively with LMR (all P < 0.001). For differentiating breast cancer from benign breast disease, sTREM-1 showed good diagnostic performance (AUC = 0.842), which improved when combined with CA15-3 and NLR (AUC = 0.889). Elevated sTREM-1 independently predicted shorter DFS in multivariate analysis (HR = 1.96, 95% CI: 1.01-3.80, P = 0.046). Conclusion: Circulating sTREM-1 is elevated in breast cancer and reflects myeloid-driven immune-inflammatory activation. As a measurable serum biomarker, sTREM-1 may provide complementary information for auxiliary diagnosis and prognosis evaluation. Larger multicenter studies are needed to validate its clinical utility and define standardized assay thresholds.