Daily physical activity monitoring in older adults with metastatic prostate cancer on active treatment: Feasibility and associations with toxicity.

INTRODUCTION: Physical activity may be associated with cancer treatment toxicity, but generalizability to geriatric oncology is unclear. As many older adults have low levels of physical activity and technology use, this area needs further exploration. We evaluated the feasibility of daily step count monitoring and the association between step counts and treatment-emergent symptoms. MATERIALS AND METHODS: Adults aged 65+ starting treatment (chemotherapy, enzalutamide/abiraterone, or radium-223) for metastatic prostate cancer were enrolled in a prospective cohort study. Participants reported step counts (measured via smartphone) and symptoms (Edmonton Symptom Assessment Scale) daily for one treatment cycle (i.e., 3-4 weeks). Embedded semi-structured interviews were performed upon completion of the study. The feasibility of daily monitoring was evaluated with descriptive statistics and thematic analysis. The predictive validity of a decline in daily steps (compared to pre-treatment baseline) for the emergence of symptoms was examined using sensitivity and positive predictive value (PPV). Associations between a 15% decline in steps and the emergence of moderate (4-6/10) to severe (7-10/10) symptoms and pain in the next 24 h were assessed using logistic regression. RESULTS: Of 90 participants, 47 engaged in step count monitoring (median age = 75, range = 65-88; 52.2% participation rate). Daily physical activity monitoring was found to be feasible (94% retention rate; 90.5% median response rate) with multiple patient-reported benefits including increased self-awareness and motivation to engage in physical activity. During the first treatment cycle, instances of a 15% decline in steps were common (n = 37, 78.7%), as was the emergence of moderate to severe symptoms overall (n = 40, 85.1%) and pain (n = 26, 55.3%). The predictive validity of a 15% decline in steps on the emergence of moderate to severe symptoms was good (sensitivity = 81.8%, 95% confidence interval [CI] = 68.7-95.0; PPV = 73.0%, 95% CI = 58.7-87.3), although the PPV for pain was poor (sensitivity = 77.8%, 95% CI = 58.6-97.0; PPV = 37.8%, 95% CI = 22.2-53.5). In the regression models, changes in daily physical activity were not associated with symptoms or pain. DISCUSSION: Changes in physical activity had modest ability to predict moderate to severe symptoms overall. Although participation was suboptimal, daily activity monitoring in older adults with cancer appears feasible and may have other uses such as improving physical activity levels. Further studies are warranted.