Lifestyle Intervention Study in Adjuvant Treatment of Early Breast Cancer

Inclusion Criteria:

Post-menopausal woman with a diagnosis of invasive breast cancer (T1-3,pN0-2,M0) for which definitive surgery was performed during the previous 36 months.
On adjuvant hormonal therapy with letrozole at time of randomization (either as initial adjuvant hormonal therapy or after a switch from tamoxifen or other hormonal therapy).
BMI ≥ 24 kg/m2.
Medical, surgical or radiation oncologist agrees to subject participation in a diet and physical activity program.

Exclusion Criteria:

Life expectancy less than five years.
Self-reported inability to walk at least 2 blocks (at any pace).
Insulin requiring diabetes (telephone directed diet and physical activity changes would be difficult in this population without close coordination with the treating physician). Non-insulin requiring diabetics are eligible for the study.
Serious digestive and/or absorptive problems, including inflammatory bowel disease and chronic diarrhea that preclude adherence to the study diet.
Cardiovascular, respiratory or musculoskeletal disease or joint problems that preclude moderate physical activity. Moderate arthritis that does not preclude physical activity is not a reason for ineligibility.
Psychiatric disorders or conditions that, in the opinion of the investigator, would preclude participation in the study intervention (e.g. untreated major depression or psychosis, substance abuse, severe personality disorder).
Patients on aromatase inhibitors other than letrozole at study entry.
Known recurrence of breast cancer (local, regional or distant) at any time prior to study entry.
History of other malignancies except: adequately treated non-melanoma skin cancer, curatively treated in situ carcinoma of the cervix, or other solid tumours curatively treated with no evidence of disease for ≥ 5 years. Prior in situ cancer of the breast is not a reason for exclusion.
Patients not fluent in either English or French (spoken and written).
Patient unwilling or unable to provide informed consent.