Impact of Vitamin D Supplementation on the Rate of Pathologic Complete Response in Vitamin D Deficient Patients

Primary Objective: To determine if pathologic complete response in vitamin D deficient patients receiving vitamin D supplementation during neoadjuvant chemotherapy for operable triple negative breast cancer is greater than or equal to 60% or less than or equal to pathologic complete response in historical controls (30%) using a one-stage phase II design. Secondary Objective(s): * To estimate the proportion of patients with residual cancer burden (RCB) classes I, II, and III in vitamin D deficient patients receiving vitamin D supplementation during neoadjuvant chemotherapy for operable triple negative breast cancer. * To estimate pathologic complete response reaction in the observational arm of vitamin D sufficient patients receiving neoadjuvant chemotherapy for operable triple negative breast cancer. * To determine the feasibility of delivery of vitamin D supplementation with standard of care chemotherapy. * To determine the safety and tolerability of the combination of vitamin D supplementation with standard of care chemotherapy. * To estimate the change in vitamin D receptor (VDR) expression from pre- and post-neoadjuvant treatment breast tumor tissue samples of vitamin D deficient patients. * To estimate the change in vitamin D receptor (VDR) expression from pre- to post-neoadjuvant treatment breast tumor tissue samples in a sample of 5 vitamin D sufficient patients. * To estimate the changes in the fecal microbiome of vitamin D deficient patients from pre- to post-neoadjuvant treatment. * To estimate the changes in the fecal microbiome in a sample of 5 vitamin D sufficient patients from pre- to post-neoadjuvant treatment. Patients will be followed for a minimum of 30 days after the last study intervention is administered for adverse events monitoring. Patients will be followed for 30 days after removal from study or until death, whichever occurs first. Patients removed from study for unacceptable adverse events will be followed until resolution or stabilization of the adverse event.