Factors associated with physical activity of breast cancer patients participating in exercise intervention

Physical activity has been known to improve survival and quality of life of patients with breast cancer. To find factors associated with physical activity, we analyzed the dataset of the multicenter controlled trial of exercise intervention.

Three hundred fifty-six participants were assigned to two groups: "Smart After-Care" (smartphone application and pedometer were provided) or exercise education only. Physical activity was measured by International Physical Activity Questionnaire-Short Form (IPAQ-SF) at baseline and after 12 weeks. The association between physical activity and other clinical characteristics was analyzed.

At baseline, physical activity amount was 2315.5 ± 3513.2 MET min/week: 33.0% inactive, 49.6% minimally active, and 17.4% health-enhancing physical activity (HEPA) active. Factors associated with HEPA include cancer stage and grip strength. A significantly lower proportion was HEPA active among those with advanced stage than among those with stage 0. After intervention, physical activity was increased to 3466.2 ± 4712.5 MET min/week: 15.3% inactive, 50.4% minimally active, and 34.2% HEPA active. Physical activity was increased in 63.4% of the participants. Factors associated with physical activity increase include cancer stage, diarrhea, and type of exercise intervention. Participants with advanced stage have a 3.3 times higher chance of increasing physical activity. Participants who received "Smart After-Care" have a 64% higher chance of increasing physical activity.

Before the intervention, participants with advanced stage are less likely to be HEPA active. Exercise intervention was more beneficial for those with advanced stage or physical symptoms. "Smart After-Care" was more effective than education only in increasing physical activity.