Pre-operative SABR With and Without Caloric Restriction for Early Stage Breast Cancer

PRIMARY OBJECTIVE: I. To detect a decrease in cellularity of the tumor in participants undergoing caloric restriction during pre-operative SABR as compared to participants undergoing SABR alone. SECONDARY OBJECTIVES: I. Change in miR-21 as defined by baseline and post radiation levels. II. Investigate measurable changes of patient and tumor characteristics from the combination of SABR and caloric restriction (CR) versus SABR alone to inform future trials. III. To describe pathologic complete response (pCR) rates as defined by no residual carcinoma or no residual invasive carcinoma, but ductal carcinoma in situ (DCIS) may be present, in each arm as well as by subtype. IV. To assess response of each treatment arm using contrast-enhanced mammography (CEM) and correlate with pathologic response. V. To describe short term surgical outcomes including: sentinel lymph node (SLN) identification rate, positive margins requiring return to the operative room for re-excision, and post-operative complications (infection, delayed wound healing, seroma requiring aspiration). VI. To measure patient reported health-related outcomes and satisfaction with outcome. VII. To compare patient reported cosmesis to physician reported cosmesis scores, where cosmesis is rated as excellent, good, fair or poor. VIII. To compare pCR rates between women randomized to SABR alone to women randomized to SABR + CR who are at least 80% adherent to the CR intervention. IX. To compare pCR rates between women randomized to SABR alone who do not deviate by more than 10% from their baseline caloric intake to women randomized to SABR + CR who are at least 80% adherent to the CR intervention. EXPLORATORY OBJECTIVES: I. Tissue: To determine the downstream molecular effects of diet related to miR-21 such as FAS/FASL, PD-1, LAG3 and STAT3 expression. II. Microbiome: Compare baseline to post-SABR microbiome species separately for each trial arm. III. Serum: Determine if anti-tumor immunity has increased with increased CD8 and decreased Treg in tumor. Compare proteomic profiles. TERTIARY OBJECTIVE: I. To determine the ipsilateral breast recurrence rate, distant disease-free interval, recurrence free survival, and overall survival. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive standard dietary recommendations. Patients undergo SABR every other day for 5 fractions. Within 4-12 weeks of completion of SABR, patients undergo surgical resection with sentinel lymph node biopsy. ARM II: Beginning 1 week before the start of SABR, patients undergo a caloric restriction diet for 6-12 weeks (for the duration of radiation treatment, until post radiation follow-up appointment) consisting of reducing calorie intake by 25%. Patients undergo SABR every other day for 5 fractions. Within 4-12 weeks of completion of SABR, patients undergo surgical resection with sentinel lymph node biopsy. After completion of study intervention, patients are followed up at 3-6 weeks, and then 6 months after surgery.