The purpose of this study is to find out what effects, if any, exercise and a plant-based diet have on aromatase levels in postmenopausal women who are overweight and being treated with an aromatase inhibitor for their HR+ breast cancer. The study will also look at other ways diet and exercise may affect your body (for example, changing the way your breast tissue expresses or makes genes) and your quality of life.

Inclusion Criteria:

• Patients with histologically-confirmed, HR-positive (ER and/or PR) stage 1-3 breast cancer

• Completed anti-HER2 therapy, if HER2-positive

• Postmenopausal status defined by lack of menses for 2 years, oophorectomy, or medical ovarian suppression

• At least 3 months post completion of chemotherapy, if administered

• At least 3 months post radiation, if administered

• Receiving adjuvant endocrine therapy with an aromatase inhibitor (anastrozole, letrozole, exemestane)

• ECOG performance status of 0 to 1

• Sedentary (i.e.,performing <150 minutes / week of exercise structured moderate-intensity or strenuous-intensity)

• Age ≥ 18

• BMI ≥ 27

• Able to achieve an acceptable peak baseline CPET, as defined by any of the following criteria and in the absence of high risk ECG findings or other inappropriate response to exercise as determined by the investigator:

  • Achieved a plateau in oxygen consumption, concurrent with an increase in power output
  • A respiratory exchange ratio ≥ 1.10
  • Attainment of maximal predicted heart rate (HRmax) (i.e., within10 bpm of age- predicted HRmax [HRmax= 220 - Age (years)]
  • Volitional exhaustion, as measured by a rating of perceived exertion (RPE) ≥ 18 on the BORG scale.

• Willingness to comply with all study-related procedures

• Intact breast available for biopsy

Exclusion Criteria:

• Presence of metastatic disease

• Any concurrent malignancy requiring active treatment with the exception of selective estrogen receptor modulators and aromatase inhibitors

• Insulin-dependent diabetes mellitus or non-insulin dependent diabetes mellitus on insulin therapy

• Enrollment onto any other interventional investigational study except interventions determined by the PI not to confound the effect of exercise or diet on study outcomes

• Mental impairment leading to inability to cooperate

• Any of the following contraindications to exercise:

  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. Respiratory failure
  15. Acute non-cardiopulmonary disorders that may affect exercise performance

• Any other condition or intercurrent illness that, in the opinion of the investigator, makes the subject a poor candidate for study participation.

• Nut or legume allergy

• Concurrent participation in weight loss programs

Breast cancer

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.