Impact of Intermittent Fasting on Biomarkers of Inflammation and Health-Related Quality of Life: A Feasibility Trial for Women With HR+/HER2- Early Breast Cancer

1. Breast cancer patients ≥ 18 years old who are willing to consent to an approximately 14-hour nighttime fasting period and an approximately 10-hour daytime eating period.

2. Histologically and/or cytologically confirmed diagnosis of estrogen receptor (ER) positive (ER+) and human epidermal growth factor receptor (HER) 2 negative (HER2-) localized breast cancer (stages I-III).

1. Progesterone receptor positive or negative patients are allowed.

2. Hormone receptor positivity is defined as ER positivity in at least 1% cells by immunohistochemistry (IHC). HER 2-negative breast cancer is defined as a negative in situ hybridization test or an IHC status of 0, 1+ or 2+. If IHC is 2+, a negative in situ hybridization fluorescence in situ hybridisation (FISH), chromogenic in situ hybridization (CISH), or silver-enhanced in situ hybridization (SISH) test is required.

3. Body mass index (BMI) ≥ 25.

4. Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2.

5. Subject must be willing to start the intermittent fasting (IF) intervention within three months of starting adjuvant endocrine therapy (AET), or at the discretion of the treating providers, and within 30 days of study enrollment.

6. Subjects who received neoadjuvant or adjuvant chemotherapy must have recovered completely from chemotherapy-related side effects such as nausea/emesis as determined by the treating providers.

7. Subjects who received neoadjuvant endocrine therapy are eligible only after completion of their definitive surgery (i.e., when ready to start adjuvant endocrine therapy) and treating provider ensures complete closure and healing of surgical incisions.

9. Subjects on a targeted therapy, such as cyclin-dependent kinase (CDK) 4/6 inhibitor, or selective estrogen receptor degrader (SERD), or other clinical trial participants in the adjuvant setting are eligible at the discretion of the treating physician.

10. Subject co-administered with any prescriptions that may cause dizziness, hypoglycemia, or hypotension need to be evaluated and deemed eligible by the treating physician.

11. Adequate hepatic, renal function and adequate bone marrow reserve as determined by the treating physician:

1. aspartate aminotransferase (AST), alanine aminotransferase (ALT) ≤ 2.5 × institutional upper limit.

2. Total bilirubin ≤ 1.5 × upper limit of normal (ULN), except for subjects with Gilbert's syndrome who may be included if their total bilirubin is ≤ 3.0 × ULN and direct bilirubin ≤ 1.5 × ULN.

3. alkaline phosphatase (ALP) ≤ 2.5 × institutional upper limit with exception that ALP of \< 5 × ULN is acceptable in patients with elevated with ALP due to bone metastases (in the absence of liver metastases).

4. Serum creatinine \<1.5 × ULN.

5. Absolute neutrophil count (ANC) ≥1000/µL.

6. Subjects with lymphopenia are eligible at the discretion of the treating provider.

i. Hemoglobin (Hb) ≥ 8g/dL. ii. Platelet count ≥ 100,000/µL.

12. Premenopausal woman:

1. Premenopausal is defined as someone who has had menses at any time in the last 12 months. For premenopausal women who are eligible for this trial, the treating physician may choose to monitor ovarian function with laboratory tests e.g., follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol as clinically indicated to assess their menopausal status.

2. Subjects must agree not to conceive throughout the study and must use accepted methods of contraception.

3. Women of childbearing potential must have a negative pregnancy test within seven days of registration and or seven to 10 days prior to starting study treatment.

13. Subjects who have an atypical sleep-wake schedule or different eating schedules are eligible at the discretion of the study investigators and dietitians as long as they agree to nightly fasting.

14. Ability to understand a written informed consent document, and the willingness to sign it.

What this study is about