Impact of Ketogenic Diet on Tumor Microenvironment in Patients With Breast Cancer

After screening for eligibility participants will meet with a dietitian who will provide education on a ketogenic diet (KD) along with additional educational material. Patients will adhere to a ketogenic diet for 3 weeks. Serum glucose and ketones will be measured by patients daily to assess adherence to KD. Patients will also keep a daily diary that will note food intake along with physical activity.

Inclusion criteria

• Be willing and able to provide consent for the study
• Age ≥ 18 on the day consent is obtained
• Eastern Cooperative Oncology Group (ECOG) score ≤ 2
• Patients must be postmenopausal the time of study entry
• Stage I or II breast cancer using Tumor, Nodes and Metastasis (TNM) stage groups per American Joint Committee on Cancer (AJCC) 8th edition
• Plan for upfront breast surgery with mastectomy or partial mastectomy and does not require pre-operative systemic therapy per standard of care
• Must have tissue available from initial breast biopsy performed per standard of care
• have the ability in the opinion of the investigator to adhere to a ketogenic diet and comply with study requirements such as ability to participate in telemedicine, utilize apps on a smart device, measure glucose/ketones at home, accurately log food intake and exercise, prepare food that is in line with ketogenic diet

Exclusion criteria

• Clinical indication for neoadjuvant therapy
• Partial mastectomy or mastectomy planned for less than 3 weeks from study entry
• Inability to comply with ketogenic diet
• Consistent use of ketogenic diet within past 3 months
• Participation in another diet program during study period
• Nonepithelial breast malignancy such as sarcoma or lymphoma
• Body Mass Index < 18.5
• Comorbidities and/or active or ongoing illness that in the opinion of the investigator will limit patient's ability to safely participate in study
• Type I diabetes
• Use of insulin or other oral hypoglycemic drugs for diabetes
• Has had any of the following within the past 6 months

• Myocardial infarction or unstable angina
• Ventricular arrythmia
• Acute decompensated heart failure
• Cerebrovascular accident
• Hypertensive emergency
• Uncontrolled hypertension despite antihypertensive use
• End-stage renal, liver, or cardiac disease
• genetic disorders that affect lipid metabolism (example: pyruvate carboxylase deficiency, porphyria, primary carnitine deficiency, carnitine palmitoyltransferase I or II deficiency, carnitine translocase deficiency, beta-oxidation defects, among others)
• G6PD (glucose-6-phosphate dehydrogenase) deficiency
• Malabsorption syndromes (such as but not limited to inflammatory bowel disease, history of gastric sleeve, prior bowel resection)
• History of recurrent kidney stones or predisposition to kidney stones
• Triglycerides ≥ 500
• Has known psychiatric or substance use disorders that would interfere with participation in the study