Association of Baseline Serum DKK-1 Levels with Subsequent Bone Metastasis in Stage III Breast Cancer

Background and Objectives: Bone metastasis is the most frequent site of distant spread in breast cancer, yet reliable biomarkers capable of identifying patients at increased risk before metastatic disease becomes clinically evident remain limited. We investigated whether baseline serum Dickkopf-1 (DKK-1) and irisin levels were associated with subsequent bone and liver metastasis in patients with stage III breast cancer. Materials and Methods: Sixty-three patients with stage III breast cancer were retrospectively included. DKK-1 and irisin concentrations were measured using enzyme-linked immunosorbent assay in archived serum samples collected at the time of initial diagnosis, before the start of definitive treatment. Associations between biomarker levels and subsequent metastatic outcomes were evaluated using maximally selected rank statistics for cut-off determination, Kaplan-Meier survival analysis, restricted cubic spline analysis, and Cox proportional hazards regression models.