CTNI-45. EXTENDED SURVIVAL IN RECURRENT GLIOBLASTOMA TREATED WITH TTFIELDS AND RADIOSURGERY GUIDED BY EARLY TYROSINE-PET: RESULTS FROM THE TTARGET TRIAL

Abstract BACKGROUND Recurrent glioblastoma (rGBM) is highly aggressive, and treatment options are limited. The TTaRGeT trial evaluated the efficacy and safety of combined tumor treating fields (TTFields) and stereotactic radiosurgery (SRS) guided by fluorine-18-fluoroethyl-L-tyrosine positron emission tomography (tyrosine-PET) in patients with rGBM. METHODS In this prospective, single-arm trial, 40 patients with recurrent glioblastoma were treated with TTFields and tyrosine-PET-guided SRS. The primary outcome was one-year overall survival (OS) compared to propensity-matched historical controls from the EF-11 trial [cohort 1 (n=40) and first recurrence (cohort 2, n=13)]. Secondary outcomes were progression-free survival, toxicity profile, steroid needs until treatment failure, patterns of failure, and objective response rates (ORR). RESULTS The one-year survival rate was 67.5% (95%CI 50.7-79.7) for patients treated with SRS and TTFields compared with 21.6% (95%CI 10.0-35.3) for matched cohort 1 (n=40) and 14.3% (95%CI 0.7-46.5, p < 0.001) for cohort 2 (n=13), 87.5% of patients showing stabilization or reduced tumor enhancement in T1-GAD images. Radiation induced contrast-enhancement was detected in 42.5% of patients but was grade >1 in only 1 case, and 35% of patients required no steroids by the end of the study. While 116/474 (25%) events were classified as probably treatment-related, grade 3 or higher treatment-related toxicities were uncommon, and there was no treatment-related mortality.Overall survival among the patients who received TTaRGET reached a plateau of 32% at 30 months. CONCLUSIONS The combination of TTFields and tyrosine-PET-guided SRS significantly improves survival and tumor control in rGBM patients compared to historical controls.Integration of external control data, with patient-level information, has the potential to accelerate the development and improving decision making FUNDING Novocure (Baar, Switzerland) provided funding and device support and had no influence on study design, data analysis, or reporting.