PRIMARY OBJECTIVES:~I. To assess the safety of the experimental intervention based on the frequency of occurrence of a dose limiting toxicity (DLT) in the first 14 participants assigned to the experimental treatment arm.~II. Evaluate the difference in post-treatment Ki67 labeling index (LI) in cancer adjacent ductal carcinoma in situ (DCIS) (in the presence of invasive breast cancer [IBC]), if present, or intraepithelial neoplasia (IEN) (defined as atypical ductal hyperplasia [ADH] or atypical lobular hyperplasia [ALH] or lobular carcinoma in situ [LCIS]) between the active treatment and the control group.~SECONDARY OBJECTIVES:~I. To explore the effect of intervention on the change of expression of PP2A-GSK3beta-MCL-1 axis in pre-post treatment cancer tissue levels.~II. To measure the change in circulating biomarkers: Homeostatic model assessment (HOMA) index, highly sensitive C-reactive protein (CRP) (hsCRP), C-peptide, IGF-I, IGFBP-1, IGFBP-3, free IGF-I, Hb1Ac, lipid profile, adipokines (leptin and adiponectin).~III. To correlate a customized next generation sequencing (NGS) mutational profile panel focused on estrogen receptor (ER) positive (+ve) with the response of Ki67.~IV. To measure the difference of cell death by immunohistochemistry (IHC) for M30 in post- treatment cancer samples between arms.~V. To measure the difference of phosphorylated (p)S6 by IHC in post- treatment cancer samples between arms.~VI. To assess safety and toxicities according to National Cancer Institute (NCI)-Common Terminology Criteria for Adverse Events (CTCAE) version (v.) 5.0.~VII. To correlate physiological distress, eating habits, tobacco and alcohol consumption with the response of Ki67 between arms.~VIII. To compare the area under the curve (AUC) of glucose levels between arms and within the experimental arm according to different doses of metformin hydrochloride extended release (0 mg, 750 mg and 1500 mg).~OUTLINE: Patients are randomized to 1 of 2 arms.~ARM I: Patients fast for >= 16 hours every night and use the continuous glucose monitoring system for 4-6 weeks. Patients also receive nutritional counseling sessions on days 0 and 10. Beginning week 2, patients also receive metformin hydrochloride extended release orally (PO) once daily (QD) until the day of surgery. Treatment continues for 4-6 weeks (until surgery) in the absence of disease progression or unacceptable toxicity. Patients undergo the collection of blood samples at baseline and at the final study visit (days 28-43), and the collection of tissue at the time of surgery (days 28-43).~ARM II: Patients continue their usual dietary pattern and use the continuous glucose monitoring system for 4-6 weeks (until surgery). Patients undergo the collection of blood samples at baseline and at the final study visit (days 28-43), and the collection of tissue at the time of surgery (days 28-43).~After completion of study intervention, patients are followed up at 30 days.
This phase IIb trial studies the combined effect of prolonged nightly fasting and metformin hydrochloride extended release in decreasing breast tumor cell proliferation and other biomarkers of breast cancer. Preventing invasive breast cancer or DCIS. Metformin is widely used to treat type II diabetes and is associated with a decreased risk of cancer and death in diabetic individuals. Intermittent fasting may protect cancer patients from the toxic effects of chemotherapy agents without causing chronic weight loss. The combination of intermittent fasting and metformin may reduce breast cancer growth and may be used in women at risk for breast cancer or other cancers associated with being overweight.