Response patterns of recurrent glioblastomas treated with tumor-treating fields

Abstract

Glioblastoma multiforme (GBM) is the most common form of primary malignant brain cancer. Median overall survival (OS) for newly diagnosed patients is only about 12 to 18 months. GBM tumors invariably recur, and there is no widely recognized and effective standard treatment for recurrent GBM. NovoTTF Therapy is a novel and US Food and Drug Administration (FDA)-approved antimitotic treatment for recurrent GBM with potential benefits compared with other options. Recurrent GBM patients from two prior trials with demonstrated radiologic tumor response to single-agent NovoTTF Therapy were analyzed to better characterize tumor response patterns and evaluate the associations between response, compliance, and OS. In addition, a compartmental tumor growth model was developed and evaluated for its ability to predict GBM response to tumor-treating fields (TTFields). The overall response rate across both trials was 15% (4% complete responses): 14% in the phase III trial (14/120) and 20% (2/10) in a pilot study. Tumor responses to NovoTTF Therapy developed slowly (median time to response, 5.2 months) but were durable (median duration, 12.9 months). Response duration was highly correlated with OS (r2 =.92, P