The purpose of this study is to compare normalization of vitamin D serum level after 6 months of vitamin D supplementation adjusted to baseline vitamin D serum level vs.conventional vitamin D supplementation.

Inclusion Criteria:

• Breast adenocarcinoma treated by neoadjuvant or adjuvant chemotherapy within 12 months prior to study enrollment
• WHO performance status 0-1
• Age ≥18 years old
• Affiliation to a social security regime or beneficiary of equivalent social protection
• Written informed consent provided before any study specific procedures

Complementary inclusion criterion for randomization

- Proved vitamin D deficiency as defined by serum vitamin D level lower than 30 ng/ml (75 nmol/L).

Exclusion Criteria:

• Metastatic disease
• History or presence of any other malignancy (except curatively treated nonmelanoma skin cancer or in situ cervix carcinoma) ………….

traités dans les 5 ans précédents.

• Contraindication to calcium or cholecalciferol

• Known severe hypersensitivity to vitamin D or to calcium supplementation or to one of the excipients.

• Disease and/or medical conditions accompanied by hypercalcaemia and/or hypercalciuria

• Calcium lithiasis and tissue calcification

• Hypervitaminosis D

• Presence of significant comorbidities:

  i) Uncontrolled endocrine disease ii) Known disorders of calcium phophorus laboratory testing iii) Proved osteopenia or osteoporosis requiring vitamin D and calcium supplements

• Concomitant treatment with other experimental products or another vitamin D calcium treatment

• Pregnancy, breastfeeding or of reproductive potential not using an effective contraceptive method

• Legal inability or restricted legal ability. Medical or psychological conditions not allowing proper study completion or informed consent signature