This study is being done to examine the safety and feasibility of a supervised progressive exercise program in women diagnosed with metastatic breast cancer. Previous research among women with metastatic breast cancer has shown that some of the treatments commonly used in this population may have an adverse impact on physical fitness levels leading to feelings of fatigue and poor quality of life. Supervised exercise training has been shown to reduce some of these side-effects in women with early-stage breast cancer receiving common cancer treatments. However, it is not known if supervised exercise training is a safe and feasible intervention in women with metastatic breast cancer. This study is designed to find out if supervised exercise training is safe as the patients undergo treatments for metastatic breast cancer.

Inclusion Criteria:

• MSK histologically confirmed metastatic breast cancer

• Measurable disease (or nonmeasurable bone-only disease) assessed by CT or PET/CT performed as part of standard of care, at the discretion of the attending oncologist in the Breast Medicine Service

• ≥18 years of age;

• Life expectancy >3 months;

• ECOG ≤ 1

• Sedentary, as per the leisure score index (LSI) of the Godin Leisure-Time Exercise Questionnaire (GLTEQ) . Participants who perform regular moderate or vigorous intensity exercise at least 5 days/week, for at least 30 minutes/session, are not eligible

• Able to achieve an acceptable peak baseline CPET, as defined by any of the following criteria:

  1. Achieving a plateau in oxygen consumption, concurrent with an increase in power output;
  2. A respiratory exchange ratio ≥ 1.10;
  3. Attainment of maximal predicted heart rate (HRmax) (i.e., within 10 bpm of age-predicted HRmax [HRmax = 220-Age[years]);
  4. Volitional exhaustion, as measured by a rating of perceived exertion (RPE) ≥ 18 on the BORG scale

• Normal cardiac function (left ventricular ejection fraction ≥50%);

• Medical clearance from attending oncologist indicating no relative contraindications to undergo a symptom-limited cardiopulmonary exercise test and aerobic training intervention;

• Patients with "treated and stable" brain lesions of a duration of ≥ 2 months may be enrolled

• Willing to be randomized to one of the study arms

• Female

Exclusion Criteria:

• Any of the following absolute contraindications to cardiopulmonary exercise testing:

  1. Acute myocardial infarction within 3-5 days of any planned study procedures
  2. Unstable angina
  3. Uncontrolled arrhythmia causing symptoms or hemodynamic compromise;
  4. Recurrent syncope
  5. Active endocarditis;
  6. Acute myocarditis or pericarditis
  7. Symptomatic severe aortic stenosis
  8. Uncontrolled heart failure
  9. Acute pulmonary embolus or pulmonary infarction within 3 months of any planned study procedures
  10. Thrombosis of lower extremities
  11. Suspected dissecting aneurysm
  12. Uncontrolled asthma
  13. Pulmonary edema
  14. Room air desaturation at rest ≤ 85%
  15. Respiratory failure
  16. Acute non-cardiopulmonary disorders that may affect exercise performance or be aggravated by exercise (i.e., infection, renal failure, thyrotoxicosis)
  17. Mental impairment leading to inability to cooperate.

• Any other condition or intercurrent illness that, in the opinion of the investigator, makes the participant a poor candidate for the trial

• Presence of extensive skeletal metastases, defined as more than five (5) sites of bony disease, or any symptomatic site of disease in the spine, hip, or femur. Note that, patients with more than five bony sites may be deemed eligible at the discretion of the attending oncologist.](streamdown:incomplete-link)