Physical activity and breast cancer survival: Results from the Nurses’ Health Studies
Menée à partir des données des deux cohortes "Nurses’ Health Studies" portant sur 9 308 patientes atteintes d'un cancer du sein, cette étude analyse l'association entre le type de l'activité physique pratiquée, son intensité et la mortalité spécifique ainsi que la mortalité toutes causes confondues (1 973 décès)
Background: Physical activity is generally associated with better outcomes following diagnosis; however, few studies have evaluated change in pre- to post-diagnosis activity, and repeated measures of activity by intensity and type. Methods: We evaluated physical activity and survival following a breast cancer diagnosis in the Nurses’ Health Study (NHS) and NHSII (n = 9,308 women, n = 1,973 deaths). Physical activity was evaluated as updated cumulative average of metabolic equivalent of task (MET)-hours/week (assigned per activity based on duration and intensity) and change in pre-to-post diagnosis activity. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Results: Higher post-diagnosis activity was inversely associated with breast cancer-specific mortality in categories from ≥9 MET-hours/week (vs. <3 MET-hours/week, ≥9-<18 HR = 0.74 (0.55-0.99); ≥27 HR = 0.69 (0.50-0.95), ptrend=0.04) and all-cause mortality from ≥3 MET-hours/week (≥3-<9 = 0.73 (0.61-0.88); ≥27 = 0.51 (0.41-0.63), ptrend<0.001)). Associations were predominantly observed for estrogen receptor-positive tumors and in postmenopausal women. Walking was associated with lower risk of all-cause mortality (≥9 vs. <3 MET-hours/week = 0.69 (0.57-0.84)), as was strength training. Relative to stable activity pre- to post-diagnosis (±3 MET-hours/week), increases from ≥3-9 MET-hours/week were associated with lower all-cause mortality risk (ptrend<0.001). Results were robust to adjustment for pre-diagnosis physical activity. Conclusions: Physical activity was associated with lower risk of death following diagnosis. Increased pre-to-post-diagnosis activity corresponding to ≥ 1-3 hours/week of walking was associated with lower risk of death. These results provide further impetus for women to increase their activity after a breast cancer diagnosis, though reverse causation cannot be fully excluded.
JNCI Cancer Spectrum 2022