Long-term effects of moderate versus high durations of aerobic exercise on biomarkers of breast cancer risk: Follow-up to a randomized controlled trial
Menée aux Etats-Unis auprès de 400 femmes ménopausées (durée de suivi : 1 an), cette étude analyse l'effet d'une activité physique aérobique sur la concentration sanguine de biomarqueurs associés au risque de cancer du sein
Background : The optimal lifestyle for breast cancer prevention over the long-term is unclear. We aimed to determine whether or not the amount of exercise prescribed in a year-long exercise intervention influences breast cancer biomarker levels one year later. Methods : We conducted a 24-month follow-up study (2012-2014) to the Breast Cancer and Exercise Trial in Alberta (BETA), a 12-month, two-armed (1:1), two-centre randomized controlled trial of exercise in 400 cancer-free, postmenopausal women. The exercise prescription was moderate-vigorous aerobic exercise, five days/week (three days/week supervised) for 30 minutes/session (MODERATE) or 60 minutes/session (HIGH). Participants were asked not to change their usual diet. We used linear mixed models to compare biomarker concentrations (C-reactive protein, insulin, glucose, HOMA-IR, estrone, sex hormone binding globulin, total and free estradiol) over time (0, 12, 24 months) by group (MODERATE, HIGH), using group-time interactions. Results : After 12 months of no intervention, 24-month fasting blood samples were available for 84.0% and 82.5% of MODERATE and HIGH groups, respectively (n=333/400). We found no evidence that 0-24 or 12-24 month biomarker changes differed significantly between randomized groups (HIGH:MODERATE ratio of mean biomarker change ranged from 0.97-1.06, P-values>0.05 for all). We found more favorable biomarker profiles amongst participants who experienced greater than the median fat loss during the trial. Conclusions : Prescribing aerobic exercise for 300 versus 150 minutes/week for 12 months to inactive, postmenopausal women had no effects on longer-term biomarkers. Impact: Exercise may lead to larger improvements in breast cancer biomarkers post-intervention amongst women who also experience fat loss with exercise.