Abstract BACKGROUND Functional status is a prognostic measure of survival in high grade glioma (HGG). Real-time monitoring between clinical encounters can extend the reach of care and provide actionable insights to drive more personalized and proactive care. We present data from the completed BrainWear Study, a highly novel study evaluating if data captured via a wrist-worn wearable device in patients with HGG can be used to explain, influence and/or predict cancer-related outcomes. Materials and METHODS All participants agreed to wear a wrist-worn Axivity AX3 triaxial accelerometer changed at 14-day intervals. Raw accelerometer data was processed using the UKBiobank Accelerometer analysis package v6.2.3 for Python and inclusion of high-quality wear time selected as ≥72 hours of data over 7-days. We analysed variation in activity by patient demographics and MRI result utilising the Response Assessment in Neuro-Oncology (RANO) criteria. Patient reported outcomes (PROs) were completed at planned study timepoints. Wilcoxin-signed rank test was used to compare participant activity at timepoints of stable or progressive disease (PD). Mixed-effects models were used to evaluate changes in activity. RESULTS 12512 days of accelerometer data were recorded from 56 patients (36 male; 20 female) with a median age of 60 years. 80% of the data were characterised as high-quality. Mean acceleration(mg) and time spent walking daily(h/day) correlated positively with the global health QOL and physical functioning scores and inversely with the fatigue score from PROs. In the 6-weeks surrounding an MRI scan, patients with PD walked on average 1856 steps less per day than those with stable disease, and spent 22 minutes less walking (p=0.0403). Several wearable data daily physical activity measures demonstrated statistically significant change at the time of PD. CONCLUSION Remote monitoring data can complement snapshots of health gathered during clinical visits. Collection of digital data hold promise for novel HGG trial outcome measure development.