S1 Raw data -

Purpose
Investigating the association between red cell distribution width (RDW) and all-cause mortality in patients with breast cancer, to evaluate the potential clinical prognostic value of RDW.
Methods
Based on the RDW index, patients with breast cancer in the Medical Information Mart for Intensive Care (MIMIC-IV) database were categorized into quartiles. The primary outcomes included in-hospital mortality from all causes during the first six months, the first year, and the first three years. Cox hazards regression and restricted cubic spline (RCS) models were developed to investigate the effects of RDW on primary outcomes.
Results
The study included 939 patients (female). The 6-month, 1-year, and 3-year mortality rates were 14.0%, 21.4%, and 28.4%, respectively. Multivariate Cox proportional hazards analyses demonstrated that RDW exhibited an autonomous association with an increased risk of all-cause mortality. After adjusting for confounders, higher RDW quartiles were significantly associated with 6-month mortality (adjusted hazard ratio (HR), 3.197; 95% confidence interval (CI), 1.745–5.762; P < 0.001), 1-year mortality (adjusted HR, 2.978; 95% CI, 1.867–4.748; P < 0.001), and 3-year mortality (adjusted HR, 2.526; 95% CI, 1.701–3.750; P < 0.001). The RCS curves demonstrated that high RDW (> 14.6) was associated with a greater risk of all-cause mortality. Subgroup analyses revealed no statistically significant differences in the interactions between the subgroups.
Conclusion
The study revealed a highly pronounced relationship between RDW and overall mortality, indicating its potential as an autonomous prognostic factor for increased mortality among patients with breast cancer.