ACTR-46. TUMOR TREATING FIELDS COMBINED WITH RADIOTHERAPY AND TEMOZOLOMIDE FOR THE TREATMENT OF NEWLY DIAGNOSED GLIOBLASTOMA: FINAL RESULTS FROM A PILOT STUDY
Abstract BACKGROUND Tumor Treating Fields (TTFields) are a non-invasive, loco-regional, anti-mitotic treatment comprising low intensity alternating electric fields approved for GBM. Preclinical data show that TTFields have a radio-sensitizing effect. This pilot study evaluated the safety and feasibility of TTFields/RT/TMZ in ndGBM patients. METHODS Patients with histologically confirmed ndGBM were treated with TTFields/RT/TMZ followed by maintenance TTFields and TMZ for up to 24 months. TTFields (200kHz) were delivered for >18 hours/day with removal of the transducer arrays during RT delivery. TMZ was administered at 75 mg/m2/daily for 6 weeks and RT at a total dose of 60 Gy. The primary endpoint was safety of the combined TTFields/RT/TMZ; secondary endpoints included progression-free survival (PFS), overall survival (OS) and toxicity. Adverse events (AEs) were graded per CTCAE V4.0. RESULTS Ten patients were enrolled at a single center in Israel between April and December 2017. All patients had recovered from maximal debulking surgery or biopsy. Five patients (50%) had undergone gross total resection; rest had biopsy only. Median age was 59 and median KPS was 80. Median dose of RT was 60 Gy. Six patients (60%) reported at least one AE. The most common AE was TTFields-related skin toxicity reported in 4 patients (40%), of Grade 1–2 in severity. Two patients reported serious AEs (seizures and general deterioration) considered unrelated to TTFields. Median PFS with RT/TMZ/TTFields was 10.5 months. Median OS has not been reached. CONCLUSIONS The proportion of patients with TTFields-related skin toxicity was similar to that reported in EF-14 phase 3 study (52%). No other TTFields-related toxicities were reported. There was no increase in RT- or TMZ-related toxicities with TTFields/RT/TMZ combination. A phase 2 randomized study has been initiated to investigate the efficacy of concomitant RT/TMZ/TTFields in 60 ndGBM patients.