Changes in physical activity 1 year after breast cancer diagnosis and associations with patient-reported outcomes: results from the AMBER cohort

Background: Few studies have prospectively examined how changes in physical activity in the first year after a breast cancer diagnosis may affect patient-reported outcomes (PROs) including quality of life and fatigue. Purpose: The purpose of this study was to examine changes in device-measured physical activity and associations with changes in quality of life [physical composite summary score (PCS) and mental composite summary score (MCS)] and fatigue from the first year after diagnosis among newly diagnosed women with breast cancer in the Alberta Moving Beyond Breast Cancer Study. Methods: In this prospective cohort study, we assessed women within a median of 60 days postsurgery (N= 1442) and again 1 year later (N= 1194). At both timepoints, participants wore an ActiGraph accelerometer for 7 days to measure light and moderate-to-vigorous physical activity (MVPA) and an activPAL accelerometer for daily steps. We used analysis of covariance to compare PRO change scores (dependent variables: PCS and MCS, and fatigue) across activity change quartiles (Q). Results: Participants were categorized into Q1 (decreased activity: mean changes = −37.2 minutes/day), Q2 (stable activity: mean change = −4.8 minutes/day), Q3 (modest increase in activity: mean change = 13.2 minutes/day), and Q4 (large increase in activity: mean change = +49.8 minutes/ day). For MVPA, participants in Q4 had significantly larger improvements in PCS and MCS compared with those in the lowest quartiles (PCS: Q1 Δ = 1.5 points, P = .026; Q2 Δ = 1.6 points, P = .017; MCS: Q1 Δ = 2.2 points, P = .007). Significant differences also emerged for fatigue as participants in Q4 of MVPA reported improvements in fatigue compared to those in Q1 (Δ = 1.9 points, P = .017) and Q2 (Δ = 1.9 points, P = .016). Improvements in PCS, MCS, and fatigue were observed when comparing the highest quartile of change (Q4) in light intensity activity, daily steps, and MVPA in ≥10-minute bouts to those in Q1 and Q2. Conclusions: Women with breast cancer who increased physical activity from diagnosis to 1 year had significantly better improvements in PCS, MCS, and fatigue compared with those who decreased or maintained their physical activity.