Physical activity during adolescence and young adulthood and the risk of breast cancer in BRCA1 and BRCA2 mutation carriers
Menée à partir de questionnaires auprès de 443 femmes porteuses d'une mutation BRCA1 ou BRCA2 et auprès de 443 témoins, cette étude évalue, en fonction du statut ménopausique, l'association entre une activité physique de loisir pratiquée à l'adolescence (entre 12 et 17 ans) et/ou au début de la vie adulte (entre 18 et 34 ans) et le risque de cancer du sein
Background : Physical activity is inversely associated with the risk of breast cancer among women in the general population. It is not clear whether or not physical activity is associated with the risk of BRCA-associated breast cancer. Methods : We conducted a case–control study of 443 matched pairs of BRCA mutation carriers to evaluate the association between physical activity and breast cancer risk. Moderate and vigorous physical activities at ages 12–13, ages 14–17, ages 18–22, ages 23–29 and ages 30–34 were determined using the Nurses’ Health Study II Physical Activity Questionnaire. We estimated mean metabolic equivalent task hours/week for moderate, vigorous and total physical activities overall (ages 12–34), during adolescence (ages 12–17) and during early adulthood (ages 18–34). Logistic regression analysis was used to estimate the odds ratios (OR) and 95% confidence intervals (CI) for total, moderate and strenuous recreational physical activities and breast cancer risk, by menopausal status. Results : Overall, there was no significant association between total physical activity and subsequent breast cancer risk (ORQ4 vs. Q1 = 1.01, 95% CI 0.69–1.47; P-trend = 0.72). Moderate physical activity between ages 12–17 was associated with a 38% decreased risk of premenopausal breast cancer (ORQ4 vs. Q1 = 0.62; 95% CI 0.40–0.96; P-trend = 0.01). We found no association between exercise and breast cancer diagnosed after menopause. Conclusions : These findings suggest that early-life physical activity is associated with a reduced risk of premenopausal breast cancer among BRCA mutation carriers.