This is a research study to look at blood sugar changes during chemotherapy using a continuous blood sugar monitoring device. The device uses patches that attach to the skin on the back of the arm to measure blood sugar changes for the duration of the chemotherapy course. Each patch lasts for about 2-weeks. During chemotherapy visits, new patches will be placed and will be worn until the chemotherapy course is complete. Participants will be in this study for 6 months. Approximately 50 patients will be enrolled in this study.

This is a prospective observational cohort study monitoring trends in glucose in patients with early stage breast cancer treated with neoadjuvant or adjuvant chemotherapy. Patients will wear a noninvasive glucose monitoring sensor, the Freestyle Libre Pro for the duration of chemotherapy. The primary goal of this trial is to evaluate the prevalence of hyperglycemia in patients with early-stage breast cancer during neoadjuvant/adjuvant chemotherapy. Fifty patients will be enrolled. During each chemotherapy encounter, subjects will have their glucose sensor scanned in order to download subjects' glucose data. If the sensor has become no longer adherent to the participant's skin, participants will bring the sensor with them to the chemotherapy infusion center to be scanned. During each chemotherapy encounter, the Free Style Libre sensor will be replaced by the study team. Participants who receive chemotherapy every three weeks will be asked to come in 10-14 days after their chemotherapy infusion to replace the sensor. The sensors will be worn through completion of chemotherapy (the duration will vary based on the individual's chemotherapy regimen). Patients will have fructosamine, a glucose biomarker, and serum creatinine testing at baseline and every 3 weeks (weeks 3, 6, 9, 12, 15, 18, 21, 24) until week 24 (note: week 15, 18, and 21 are optional). Patients will have additional glucose biomarker testing (hemoglobin a1c, glucose, and insulin [fasting preferred]) at baseline, week 12 and week 24. Patients will also complete questionnaires assessing for symptoms of chemotherapy induced peripheral neuropathy, quality of life, and fatigue at baseline, week 12 and week 24. Visits will be conducted within the below specified windows forbidding unexpected circumstances such as missed appointments or loss to follow-up.

Inclusion Criteria:

• Age ≥18 years
• History of stage I-III breast cancer
• Patient scheduled to receive adjuvant or neoadjuvant chemotherapy
• Signed informed consent

Exclusion Criteria:

• Current treatment with insulin
• Current treatment with non-topical steroids, with the exception of steroid treatment as a supportive chemotherapy medication
• Inability to provide informed consent

Patients with early stage breast cancer.