Elevated risks of all-cause mortality and distant metastasis in breast cancer patients with vitamin D deficiency: a population-based analysis

PURPOSE: Vitamin D plays a key role in immune and cellular regulation, and its deficiency may worsen breast cancer outcomes. This study investigates how serum 25-hydroxyvitamin D levels relate to mortality and metastasis in breast cancer patients. PATIENTS AND METHODS: This retrospective cohort study used the TriNetX database to identify 675,625 breast cancer patients aged 18 to 80 who were diagnosed between 2010 and 2020. Patients were categorized into two groups: those with vitamin D deficiency (VDD; <20 ng/mL) and those with adequate vitamin D levels (VDA; ≥30 ng/mL). A 1:1 propensity score matching was performed, resulting in two matched cohorts of 1181 patients each. Kaplan-Meier survival analysis and Cox proportional hazards models were used to evaluate 5-year clinical outcomes. RESULTS: VDD was significantly associated with higher all-cause mortality (HR: 1.970, 95% CI: 1.417-2.738; p < 0.001) and distant metastasis risk (HR: 1.523, 95% CI: 1.206-1.923; p < 0.001). Subgroup analysis discloses VDD elevated 5-year mortality and metastasis risk in breast cancer, particularly in older and obese. Our findings concluded that maintaining optimal vitamin D levels may be a valuable strategy for improving patient outcomes in breast cancer management.