The aim of the study is to evaluate the relationship between the vitamin D replacement and pathological response in patients undergoing neoadjuvant therapy according to different molecular sub types. Because of no study evaluating pathological response to neoadjuvant therapy with vitamin D replacement in patients with breast cancer.

Calcitriol, a vitamin D metabolite, inhibits cell proliferation and pathways in invitro experiments. Vitamin D affects gene expression related to breast cancer and prevents cell differentiation, growth and angiogenesis . Low vitamin D may include a high risk of breast cancer, but there are also studies reporting that patients with low vitamin D levels at the time of diagnosis show more aggressive breast cancer course . Breast cells can produce vitamin D by taking part in the formation of 1,25 OH vit D3 in vitamin D synthesis as well as in kidney cells. Apoptosis can be caused by vitamin D receptors . There are very few studies on the effect of vitamin D replacement on breast cancer-related survival. There are studies reporting the incidence of fewer breast cancer with vitamin D replacement in contrast to there are studies showing the opposite .Patients achieved pathological complete response (PCR) with neoadjuvant therapy have been shown to have better survival. There are studies showing that they do not affect the PCR ratio related to the level of vitamin D in breast cancer patients receiving neoadjuvant chemotherapy. In one study, it was shown that it increases the response rate when given with bisphosphonate .There is no study evaluating pathological response to neoadjuvant therapy with vitamin D replacement in patients with breast cancer. The aim of the study is to evaluate the relationship between the vitamin D replacement and pathological response in patients undergoing neo-adjuvant therapy according to different molecular subtypes of biopsy-diagnosed breast cancer patients.

Inclusion Criteria:

• Invasive breast cancer is confirmed by biopsy
• enough organ function,
• metabolically normal,
• eligible for neoadjuvant treatment
• The patients who were informed about the prerequisites with their consent

Exclusion Criteria:

• having metastatic disease
• having not operated from breast cancer after neoadjuvant treatment

The aim of the study was to evaluate the relationship between the vitamin D replacement and pathological response in patients undergoing biopsy-diagnosed neo-adjuvant therapy according to different molecular subtypes.