Breast Cancer Exercise Intervention Study (BREXINT)

Singapore Cancer Society, Genome Institute of Singapore, National University of Singapore, Singapore General Hospital

This is a 24-week exercise programme consisting of aerobic exercise and muscle strength training, 3 sessions per week. The first 9 sessions are supervised by physiotherapists in person, followed by 63 sessions monitored remotely (video) or supervised by trainers at ActiveSG (Sport Singapore) gyms.

This is a multi-centre, randomised controlled study of a 6-month (24-week) exercise programme versus observation in 2156 early stage and locally advanced breast cancer patients who have undergone curative breast surgery, and who have completed (neo)adjuvant chemotherapy (if given) or radiotherapy (if given). Patients are stratified by centre (NCC/SGH, NUH), menopausal status, ER/PR status, body fat/muscle ratio. Cardiorespiratory fitness, muscle strength, level of routine daily physical activity, body fat/muscle ratio are monitored during the study period. Blood is collected at baseline, 8 weeks, 16 weeks, 24 weeks, 52 weeks, then annually for 4 times. Questionnaires are periodically conducted to assess quality of life (QoL). A food diary is kept.

Eligible patients will be randomised into 2 groups: exercise (intervention group, N = 1078) and usual care (control group, N = 1078). The exercise intervention group will undergo an aerobic exercise and strength training programme.

The exercise intervention group will undergo an aerobic exercise and strength training programme, comprising 3 sessions per week, spanning 24 weeks (total: 3x24=72 sessions).

Aerobic exercise consists of 20-minute brisk walks or jogs (5-6 km/h) on the treadmill each session, reaching a heart rate corresponding to 50%-70% of the patient's VO2max (VO2max is determined before embarking on the exercise programme). Study participants are expected to aim for 50% VO2max at the start of the exercise programme, and gradually increasing to 70% VO2max in subsequent exercise sessions. Strength training comprises a series of circuit resistance exercises targeting the major muscle groups. Patients will perform 2-4 sets of these exercises each session, 8-10 repetitions per set. Both aerobic exercise and strength training are done in the same session. With warm-up and cool-down, each session is estimated to take up 1 hour.

Changes in respiratory exchange ratio (RER, unitless) during CPET, at 8, 16, and 24 weeks from baseline

Changes in weight lifted 10 repetition maximum (10-RM, Kg) for: a. Chest press; b. Latissimus pull-down; c. 2-arm curl; and d. Leg press.

Changes in absolute and relative bone mineral density (BMD, in g/cm^2) at 8, 16, and 24 weeks from baseline.

Inclusion Criteria: Patients with histologically or cytologically proven stage 1, 2, or 3 breast cancer Patients who have undergone curative breast surgery Patients who have received (neo)adjuvant chemotherapy (if given) and/or radiotherapy (if given) Females aged 21 years and older ≤ 8 weeks from breast surgery, or the last adjuvant chemotherapy or radiotherapy session, whichever is latest. Exclusion Criteria: Cardiovascular, respiratory, musculoskeletal problems that preclude moderate physical activity. Major medical problems that are deemed by the investigator to be unsuitable for enrollment.