Effect of Vitamin D Supplementation on Chemotherapy Side Effects After Adjuvant Chemotherapy for Breast Cancer

Inclusion Criteria:

1. Age between 18 and 80 years, with an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.
2. Primary diagnosis of breast cancer confirmed by preoperative pathological examination.
3. Serum 25(OH)D levels less than 20 ng/ml (50 nmol/L).
4. Patients who have not previously received chemotherapy and who plan to undergo at least 4 cycles of
5. Patients with adjuvant chemotherapy or combined targeted therapy.
6. Life expectancy of at least 6 months.
7. No other uncontrolled benign diseases at the time of recruitment.
8. All patients must have complete clinical medical records.
9. Willingness to voluntarily sign an informed consent form.

Exclusion Criteria:

1. History of invasive breast cancer.
2. Prior systemic treatment for the treatment or prevention of breast cancer.
3. Known allergic reactions to vitamin D or calcium compounds.
4. Comorbidities that may affect vitamin D or calcium balance or bone health.
5. Vitamin D or calcium supplementation in the past 3 months.
6. Presence of other tumors.
7. Pregnant or lactating women.
8. Individuals who do not wish to participate in the study.