INCIDENCE AND CHARACTERIZATION OF DERMATOLOGIC ADVERSE EVENTS IN PATIENTS TREATED WITH TUMOR TREATING FIELDS AND IMPACT ON OVERALL SURVIVAL

TTFields interfere with glioma cell division and are delivered via arrays applied to the scalp. Recommended treatment for glioblastoma involves administration of TTFields at a daily compliance rate of 75% (18 of 24 hours) to prolong OS. Given that the primary adverse effect of TTFields involves skin changes, disruptions in treatment may result from dermatologic adverse effects (dAE). Prior studies reveal an incidence of dAE between 16-43%, but they are poorly categorized. Little is known about time to onset or duration of dAE. We reviewed a cohort of patients (n=33) treated with TTFields between 2014-2017. Median duration of treatment with TTFields was 5.3 months (1.1-19.4). We identified 10 episodes of contact dermatitis, 8 erosions, 4 cases of folliculitis, and 2 ulcerations. Median time to onset of dAE was 69 days (13-123). Duration of dAE varied depending on subtype, but median duration was 64 days (13-397). Of 13 patients who developed dAE, 4 (30.8%) had a delay. Median treatment time with TTFields was 1815 hours (86 – 9446) with median daily compliance of 11.3 hours per day (0.5-22.1). Median OS of entire cohort was 8.7 months (95% CL: 7.0 – 12.1 months). Threshold analyses using Cox proportional hazards regression identified the best cutpoint for cumulative hours of treatment associated with OS. This value was used to evaluate association with incidence of dAE. Per 1000 hour increase in hours worn, HR = 0.812. The optimal cumulative hours worn identified for OS benefit is 2987 hours. The risk of death in those with at least 2987 cumulative hours worn is 0.208 times the risk of death in those with fewer hours worn. Of 13 patients with dAE, 4 (66.7%) received greater than 2987 total hrs. Comparatively, of 20 patients without dAE, only 2 (10.0%) received greater than 2987 hrs (p = 0.1824).