Plasma Vitamin C Levels in Distinguishing Benign from Malignant Breast Tumors and Clinical Correlates in Chinese Patients: A Cross-Sectional Study

BACKGROUND: Breast cancer is the most common malignancy in women globally, with rising incidence and earlier onset. Vitamin C, an essential micronutrient, plays critical roles in immune regulation and antioxidation, and cancer patients often exhibit lower plasma levels. AIM: To assess plasma vitamin C as a predictive biomarker for breast cancer and its clinical relevance. METHODS: From January to July 2025, 115 patients with benign breast tumors and 131 breast cancer patients were enrolled. Inclusion criteria were age >18 years and no regular vitamin C supplementation in the prior three months. Exclusion criteria included recent high-dose vitamin C supplementation and pregnancy. Fasting blood samples were collected prior to surgery for benign tumor patients, and 21 days after discharge (immediately before the next chemotherapy cycle) for breast cancer patients. Plasma vitamin C concentrations were quantified using UPLC-MS/MS. Clinical data, including demographics, tumor characteristics, and treatment-related parameters, were recorded. Statistical analyses were performed using SPSS 27.0. RESULTS: Plasma vitamin C concentrations were significantly lower in breast cancer patients (median 0.72 μg/mL) compared to benign tumor patients (mean 4.06 μg/mL). In benign patients, vitamin C levels negatively correlated with BMI. In breast cancer patients, vitamin C levels were significantly associated with TNM stage, pathological type, and number of metastatic sites. Hematocrit, platelet distribution width, triglycerides, and hemoglobin significantly correlated with plasma vitamin C levels. Patients receiving anthracycline-based chemotherapy had the lowest vitamin C levels, and severe adverse effects (grade ≥3) were linked to further reductions. CONCLUSION: Plasma vitamin C levels are significantly lower in breast cancer patients than in benign tumor cases, correlating with disease severity, chemotherapy regimens, and adverse effects. Our findings identify plasma vitamin C as a potential dual-utility biomarker for distinguishing malignant tumors and predicting chemotherapy-related toxicity, suggesting its therapeutic potential as a nutritional modulator.