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

The purpose of this study is to test whether four different supportive care programs can
reduce fatigue in women with advanced or metastatic breast cancer who are receiving a
medication called a CDK4/6 inhibitor (palbociclib, ribociclib, or abemaciclib) alongwith
endocrine therapy with or without a PI3K or AKT inhibitor.

Inclusion Criteria:

1. Women

2. Able to provide written informed consent

3. Able to speak, read, and understand English or Spanish

4. Postmenopausal (including concurrent use of ovarian suppression)

5. Diagnosis of ER+ and/or PR+, hormone estrogen receptor-2 (HER-2)- or HER-2+
metastatic or locally advanced unresectable breast cancer

6. 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.

7. 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

8. Having not consistently engaged in resistance training 2 or more days per week over
the past 3 months

9. 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

10. Approval from a medical oncology provider to participate.

Exclusion Criteria:

1. Unable to provide consent

2. Unable to read or understand English or Spanish

3. Dependent on supplemental oxygen

4. Unstable cardiac disease

5. Insulin-dependent diabetes

6. Unable to walk 2 blocks without assistance (excluding canes)

7. Regularly maintaining a shiftwork schedule, i.e. working evening shifts, night
shifts, or rotating shifts in the last 3 months

8. History of a clinical eating disorder

9. Unstable bone metastases

10. 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.

11. Presence of a severe medical condition or psychiatric condition or medications that
would preclude participation of the study intervention.