Prolonged Overnight Fasting and/or Exercise on Fatigue and Other Patient Reported Outcomes in Women With Hormone Receptor Positive Advanced Breast Cancer

Inclusion criteria

• Women
• Able to provide written informed consent
• Able to speak, read, and understand English or Spanish
• Postmenopausal (including concurrent use of ovarian suppression)
• Diagnosis of ER+ and/or PR+, hormone estrogen receptor-2 (HER-2)- or HER-2+ metastatic or locally advanced unresectable breast cancer
• Initiation of endocrine therapy in combination with a CDK4/6 inhibitor (e.g., palbociclib, ribociclib, or abemaciclib), with or without hormone estrogen receptor-2 (HER2)-directed therapy (e.g., trastuzumab ± pertuzumab), or in combination with both a CDK4/6 inhibitor and a Phosphoinositide 3-kinase (PI3K) or Protein kinase B (AKT) inhibitor, within the past 90 days.
• a) Participants who switch from one CDK4/6 inhibitor to another due to toxicity or insurance constraints remain eligible, provided enrollment occurs within 90 days of initiating the subsequent CDK4/6 inhibitor in the metastatic or locally advanced setting.
• Having not consistently (not equal to or more than 50% of the time) engaged in more than 90 minutes of moderate or 45 minutes of vigorous physical activity per week over the past 3 months
• Having not consistently engaged in resistance training 2 or more days per week over the past 3 months
• Having not consistently (not equal to or more than 50% of the time) engaged in structured fasting (i.e., not regularly fasting for ≥12hr/night) for the past 3 months
• Approval from a medical oncology provider to participate.

Exclusion criteria

• Unable to provide consent
• Unable to read or understand English or Spanish
• Dependent on supplemental oxygen
• Unstable cardiac disease
• Insulin-dependent diabetes
• Unable to walk 2 blocks without assistance (excluding canes)
• Regularly maintaining a shiftwork schedule, i.e. working evening shifts, night shifts, or rotating shifts in the last 3 months
• History of a clinical eating disorder
• Unstable bone metastases
• More than 90 days since initiation of endocrine therapy in combination with 1) a CDK4/6 inhibitor, with or without HER2-directed therapy, or 2) a CDK 4/6 inhibitor in combination with a PI3K/AKT inhibitor, in the metastatic or locally advanced.
• Presence of a severe medical condition or psychiatric condition or medications that would preclude participation of the study intervention.