Exploring factors that influence Vitamin D deficiency continuum across breast cancer patients’ care: insights from a tertiary health population

Vitamin D deficiency has prognostic implications in breast cancer care. Identifying patients at high risk for vitamin D deficiency across the breast cancer care continuum can improve testing and supplementation strategies. This study aimed to describe serum vitamin D distributions in patients receiving breast cancer care and to identify predictors of vitamin D deficiency. Method A retrospective cross-sectional analysis of 14,773 patients with at least one serum 25-hydroxyvitamin D (25(OH)D) measurement was performed. Patients were categorized into three breast diagnostic groups based on their ICD-10 code: current breast cancer (C50), screening (Z12.39), and personal history (Z85.3). 25(OH)D levels were classified as deficient (<20 ng/mL), insufficient (20–29.9 ng/mL), and sufficient (≥30 ng/mL), with severe deficiency defined as <10 ng/mL and <15 ng/mL. One-way ANOVA compared the mean of 25(OH)D levels across different breast diagnostic groups. Multivariable logistic regression examined predictors of low 25(OH)D levels (<10 ng/mL and <15 ng/mL), adjusting for age, breast diagnostic group, and ethnicity. Result Of the 14,773 patients, 99.8% were female, with a mean age of 54.8 ± 12.9 years. The overall mean serum 25(OH)D concentration was 37.3 ± 19.5 ng/mL. Serum 25(OH)D levels were higher in patients with current breast cancer (42.1 ng/mL) and those with a personal history (42.5 ng/mL) than in screening attendees (35.7 ng/mL). Significant differences among the groups were confirmed by ANOVA (F(2, 14,770) = 152.2, p < 0.0001). Overall, 14.4% were deficient (<20 ng/mL), with 6.8% severely deficient (<15 ng/mL). Severe deficiency was most common in Z12 (7.6%), followed by C50 (4.2%) and Z85 (3.4%). Increasing age was protective against deficiency, with each 10-year increase reducing the odds (aOR = 0.88 for <10 ng/mL; aOR = 0.84 for <15 ng/mL). Women with breast cancer had lower odds of deficiency than screening patients (C50: aOR 0.66; Z85: aOR 0.56). Hispanic women had higher odds of deficiency at <15 ng/mL (aOR 1.44) than non-Hispanic women. Conclusion Vitamin D deficiency is prevalent among younger women, those undergoing breast cancer screening, and Hispanic women. Targeted testing by age, diagnostic group, and ethnicity has the potential to optimize resource allocation for at-risk patients and improve supplementation strategies throughout the breast oncology care continuum.