Study of Vitamin D Supplementation Tailored to Vitamin D Deficiency in Breast Cancer Patients

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