Abstract: Background: Vitamin D is increasingly being recognized for a role beyond calcium homeostasis, with accumulating evidence suggesting it may influence the prognosis of breast cancer. The current study aimed to investigate whether serum vitamin D levels affect prognosis in breast cancer patients by modifying several prognostic factors, such as tumour grade, stage, receptor status, and lymph node involvement.

Methods: A prospective study was conducted on 120 breast cancer patients. Serum 25-hydroxyvitamin D levels were measured at diagnosis and categorized as deficient (<20 ng/mL), insufficient (20–30 ng/mL), or sufficient (>30 ng/mL). Statistical analysis was done to check the correlation between vitamin D levels and prognostic factors.

Results: Patients with normal vitamin D concentrations had significantly lower grades of tumours, smaller-sized tumours, and less lymph node positivity when compared with patients with deficient levels (p < 0.05). Vitamin D sufficiency was also associated with favorable receptor profiles, including higher rates of estrogen receptor positivity.

Conclusion: These results open a very promising window where vitamin D would emerge as the first modifiable prognostic factor for breast cancer, so there is definitely a lot more research needed on therapeutic and preventive perspectives.