Changes in objectively measured activity behavior among women undergoing breast cancer treatment: Longitudinal cohort study

Purpose: Activity behaviors of breast cancer survivors (BCSs) during treatment are unlikely to be at levels sufficient enough to gain health benefits. Previous activity research among BCSs has been mainly posttreatment and generally cross-sectional. This study aimed to determine the prevalence and changes in objectively measured moderate-to-vigorous physical activity (MVPA), light physical activity (LPA), and sedentary behavior (SED) among BCSs undergoing adjuvant/palliative therapy. Methods: Participants completed baseline surveys and wore accelerometers to measure activity during waking hours during treatment and again 6 months later. Hierarchal linear modeling (HLM) was used to determine changes. Results: In total, 77 BCSs participated. Ninety-one percent provided physical activity (PA) data for 3 or more valid days at baseline (T₁) and 72% at 6 months (T₂); 29% met PA guidelines at T₁ and 41% at T₂. Daily LPA and SED did not change from T₁ to T₂ (133 vs 138 minutes; 595 vs 597 minutes). Controlling for body mass index at the intercept, HLM revealed that MVPA significantly increased from T₁ to T₂ (+5.62; P =.015). Conclusion: An increase in objectively measured total daily MVPA over 6 months was found, at which time, fewer BCSs were currently receiving chemo- or radiotherapy and may theoretically be feeling better. However, fewer T₂ measures may bias and artificially inflate the results. Although total MVPA minutes increased at T₂, less than half BCSs were meeting guidelines and had high amounts of LPA/SED during treatment, with insignificant change over time (71% at T₁; 59% at T₂). Practitioner intervention may help reduce SED while increasing LPA and MVPA behavior among those currently undergoing treatment.