Abstract
2080 Background: The NovoTTF-100A device emits tumor treating electric fields and was tested against Best Physician’s Choice (BPC) chemotherapy in a randomized phase III trial. We analyzed post hoc the characteristics of responders and non-responders in both cohorts. Methods: Macdonald criteria were used to determine tumor response and progression. Kaplan-Meier and Chi-squared statistics were computed for time to response, response duration, progression-free survival (PFS) with and without Simon-Makuch correction, and overall survival (OS). Prognostic factors were compared using the Wilconox rank sum test. Relative hazard rates for responders and non-responders were plotted. Results: The median response duration was 7.3 versus 5.6 months for NovoTTF-100A and BPC chemotherapy respectively (p=0.0009). Five of 14 NovoTTF-100A responders but none of 7 BPC responders had prior low-grade histology. The mean cumulative dexamethasone dose was 35.9 mg for responders versus 485.6 mg for non-responders in the NovoTTF-100A cohort (p<0.0001) as compared to 525.6 mg for responders and 431.0 mg for non-responders in the BPC cohort (p=0.9520). Hazard rate analysis showed delayed tumor progression in responders compared to non-responders. The Simon-Makuch conditional plot, which adjusted for unequal progression-free states, still showed longer PFS in responders than non-responders treated with NovoTTF-100A (χ2=11.5, P=0.0007) or BPC chemotherapy (χ2=5.2, P=0.0222). The median OS was 24.8 months for responders that is longer than 6.2 months for non-responders treated with NovoTTF-100A (χ2=25.7, P<0.0001). In the BPC chemotherapy cohort, the median OS was 20.0 months for responders and 6.8 months for non-responders (χ2=5.1, P=0.0235). There was strong Pearson correlation between response and OS in NovoTTF-100A (P<0.0002) but not in BPC cohort (P=0.2952). Conclusions: Response duration, adjusted Simon-Makuch PFS and OS favor NovoTTF-100A over BPC chemotherapy. Data on prior low-grade histology and dexamethasone dose suggest potential genetic and epigenetic determinants of NovoTTF-100A response. Clinical trial information: NCT00379470.
Highlights
IntroductionObjective response rates to alkylating chemotherapy are low, ranging 5–8% [1, 2]
Patients with recurrent glioblastoma have poor prognosis
Cancer Medicine published by John Wiley & Sons Ltd
Summary
Objective response rates to alkylating chemotherapy are low, ranging 5–8% [1, 2]. Bevacizumab has a remarkably high response rate of 25–60% [3], its ability to prolong the overall survival (OS) of patients in the recurrence setting is marginal and it still awaits testing in a randomized clinical trial [4, 5]. Those who failed bevacizumab are unlikely to respond to subsequent therapy [6, 7].
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