Factors predicting long-term physical activity of breast cancer survivors. 5-year-follow-up of the BREX exercise intervention study.

Background: The benefits of exercise training are well documented among breast cancer (BC) survivors. Patients decrease their physical activity during treatment, and many fail to regain their previous exercise levels. There is therefore a need to define factors supporting long-term physical activity behavior in this patient group, to target supporting interventions aimed at preventing the decline in physical activity (PA).

Aim: The aim of this study was to determine physical and psychosocial factors explaining long-term physical activity after the adjuvant treatments in BC survivors.

Methods: Four-hundred forty-six BC survivors followed for 5-years within a randomized exercise trial participated. Factors explaining (1) physical activity after the adjuvant treatments and (2) changes in physical activity in long-term were analyzed using linear regression models and general estimating equation models. Pretreatment leisure-time physical activity (LTPA), demographic, and treatment factors, physical fitness, and quality of life (Qol) at baseline were independent factors.

Results: Exercise levels increased during the first year, and thereafter remained mostly stable. Higher LTPA, higher fitness level, better Qol and older age at baseline were associated with higher physical activity level after adjuvant treatments ( < .001) in multivariate analysis. Higher levels of fatigue ( < .008) and better emotional functioning ( = .017) at baseline were the main factors associated with increased physical activity during the follow-up.

Conclusion: Previous exercise habits and Qol after adjuvant chemo-, and radiotherapy were the strongest determinants of long-term physical activity levels in breast cancer survivors. Patients with better emotional functioning increased their exercise activity most as did those patients with higher fatigue levels at baseline. Patients suffering from fatigue after adjuvant treatment managed to increase their exercise levels, in contrast to patients with low emotional functioning, and may benefit from physical exercise interventions. Emotionally deprived patients may benefit from psychosocial support to regain their previous exercise levels.