Vitamin D Supplementation for Triple Negative Breast Cancer

Inclusion Criteria: * Women or men with histologically confirmed invasive mammary carcinoma. * Known triple negative ER/PR/HER2 receptor status as defined by: * ER and PR less than or equal to 10% and HER2 negative based on one of the following: * IHC 0 or 1+ * IHC 2+ and FISH negative * IHC 2+ and FISH equivocal and no indication for HER2 targeted therapy based on the treating investigators discretion (i.e., HER2: CEP17 ratio \< 2.0 or HER2 total copy number \<6) * Patients who plan to undergo neoadjuvant chemotherapy prior to definitive surgical management. Participants are eligible up to 2 weeks after initiating neoadjuvant chemotherapy. * ECOG performance status of 0, 1 or 2. * Age ≥ 18. * The effects of high dose vitamin D on the developing human fetus are unknown. For this reason, women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. * Ability to understand and the willingness to sign an IRB-approved informed consent document (either directly or via a legally authorized representative). Exclusion Criteria: * Patients with nephrolithiasis within the past year. * Patients with known sarcoidosis. * Patients with corrected calcium \>10.5 mg/dL within 30 days prior to initiation of chemotherapy. * History of allergic reactions attributed to compounds of similar chemical or biologic composition to vitamin D. * Pregnant women are excluded from this study because vitamin D supplementation greater than the recommended daily allowance (RDA) is a pregnancy class C agent with no adequate or well controlled studies in humans. * Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with high dose vitamin D (greater than RDA), women who are breastfeeding are excluded from this study. * Prior treatment for this malignancy including surgery, radiation therapy, chemotherapy, hormonal therapy or investigational agent prior to study entry. * Patients currently taking Vitamin D at a dose of 50,000 International Units (IU) once weekly.