ATNT-19: TUMOR TREATING FIELDS WITH CHEMOTHERAPY COMPARED TO CHEMOTHERAPY ALONE IN GLIOBLASTOMA PATIENTS AT FIRST RECURRENCE: A POST-HOC ANALYSIS OF THE EF-14 TRIAL

BACKGROUND: Tumor Treating Fields (TTFields) are an anti-mitotic, physical treatment modality. An interim analysis of the phase 3 trial comparing TTFields with temozolomide (TTFields/TMZ) to temozolomide alone (TMZ alone) showed superior progression free and overall survival in patients with newly diagnosed GBM treated with TTFields. METHODS: After completion of radiotherapy with concomitant temozolomide, patients were randomized (2:1) to TTFields/TMZ or TMZ alone. Patients who progressed on TMZ were allowed to receive a second line chemotherapy. TTFields/TMZ patients could continue TTFields with a second line chemotherapy. We analyzed baseline characteristics, choice of chemotherapy and overall survival (OS) in patients who progressed after TMZ and tested the effect of TTFields/chemotherapy compared to chemotherapy alone on OS. RESULTS: 466 pts were randomized to TTFields/TMZ and 229 to TMZ alone. Data cutoff date was December 29, 2014 and median follow up was 12.6 months. 144 and 60 patients had progressed on TMZ or TTFields/TMZ, respectively, at the time of this analysis. Baseline characteristics between 1st recurrence patients were generally well balanced, including choice of chemotherapy. Recurrent GBM patients treated with TTFields/chemotherapy lived significantly longer than on chemotherapy alone (median OS: TTFields/chemotherapy = 11.8 months; chemotherapy alone = 9.2 months; Hazard Ratio = 0.70 (95%CI 0.48-1.00); Log Rank p = 0.049). In the 43% of patients who received bevacizumab (with or without a cytotoxic chemotherapy) as their second line treatment choice TTFields/bevacizumab led to a significantly longer OS than bevacizumab without TTFields (median OS: TTFields/bevacizumab = 11.8 months; bevacizumab alone 9.0 months; Hazard Ratio = 0.61 (95%CI 0.37-0.99) Log Rank p = 0.043). CONCLUSIONS: This post-hoc analysis suggests that recurrent GBM patients treated with combined TTFields and chemotherapy and/or bevacizumab live significantly longer than on chemotherapy and/or bevacizumab alone. Prospective trials combining TTFields with chemotherapy are warranted to validate these findings.