Background: The feasibility and utility of wearable devices is unknown in sarcoma patients (pts). Objective assessment of activity level, body composition, and PROs facilitate understanding of the tolerability and toxicity of cancer treatment. Methods: From 6/11-10/12/2020, we enrolled sarcoma pts receiving systemic therapy to a prospective study evaluating activity levels and sleep via a Fitbit Charge 3, body composition with the Inbody 570, and PROs using NIH PROMIS short forms (fatigue, pain, physical function, and sleep disturbance), the Generalized Anxiety Disorder Scale, and the Patient Health Questionnaire Depression Scale. Time on study was 12-16 weeks depending upon treatment. The Fitbit was worn continuously. Body composition and PROs were assessed every 3-4 weeks. Feasibility was defined as successful device wearing and data syncing. Data was collected through a cloud-based application, Fitabase. Results: 22 pts were approached and enrolled. Two pts did not complete the first study assessment due to disease progression and were excluded from analysis. 50% of pts were female. 90% of pts were white. Median age was 47 yrs (range 20-81). The most common histologies were Ewing sarcoma and leiomyosarcoma. 89.5% (17/19) of pts wore the Fibit for >3 weeks; median time was 68 days (5-112). 95% (19/20) of pts were able to sync data. Median step count was 2614 steps (376-19806). High step counts, defined as greater than the median, were associated with improved sleep (p=0.14) and physical function (p=0.22), and decreased pain (p=0.15), but these associations were not statistically significant. Low step counts, defined as lower than the median, were associated with skeletal muscle mass loss (p=0.22), but this was not statistically significant. Conclusions: Incorporating a fitness tracker is feasible in sarcoma pts receiving systemic therapy. It provides longitudinal, objective evaluation of activity levels and sleep patterns. Correlation of activity level with sleep, body composition, and PROs was limited due to small numbers; however, a larger prospective pilot study is ongoing.

*Angiosarcoma, malignant peripheral nerve sheath tumor, myxofibrosarcoma, osteosarcoma, solitary fibrous tumor, and synovial sarcoma.