Evidence Builds for Electric Field Therapy in Recurrent GBM

Susan Pannullo, MD

A wearable device that uses electric fields to disrupt the activity of cancer cells has demonstrated survival benefits among patients with recurrent glioblastoma multiforme (GBM) in real-world settings, particularly among individuals treated in earlier stages of progression, according to data reported at recent medical meetings.

Retrospective analyses of outcomes among 457 US patients who used the NovoTTF-100A System indicate a median overall survival (OS) benefit of 9.6 months among the entire population¹ and 20 months among a subgroup of 125 patients treated with the device after their first recurrence.²

Those results are better than the findings from the pivotal clinical trial that helped pave the way for the system’s 2011 FDA approval.³ Novocure, the company developing the system, has launched a phase III trial evaluating NovoTTF plus temozolomide in patients with newly diagnosed GBM (NCT00916409).

Outcomes among patients who have used the device thus far compare favorably with historical outcomes from all other treatments for recurrent GBM, the company contends.

Typically, the median survival for patients with GBM “rarely exceeds 6 months” from the point of recurrence, said Susan Pannullo, MD, director of Neuro-Oncology in the Department of Neurological Surgery at New York-Presbyterian Hospital/ Weill Cornell Medical Center.

Pannullo discussed recent NovoTTF data and their implications in recurrent GBM during a May 21 webcast sponsored by Novocure. Data from the company’s PRiDE patient registry were included as an electronic abstract1 at the 2014 American Society of Clinical Oncology (ASCO) Annual Meeting in June and as an oral presentation at the 16th Biennial Canadian Neuro-Oncology Meeting in Halifax.²

The NovoTTF therapy offers a fresh option for battling a tumor type where there have been few new therapies during the past 40 years, Pannullo said. “It is an unusual type of treatment and it really brings the world of engineering into the world of medicine,” she said. “More and more, those two worlds are becoming closer and closer.”

System Components

The main components of the NovoTTF system are a generator that produces low-intensity alternating electrical fields called tumor treating fields (TTFs) and a transducer array composed of insulated electrodes applied directly to the patient’s scalp. The array placement is customized for each patient using the individual’s MRI scans so that normal cells are spared, Pannullo noted.

Components of the NovoTTF System

The system is designed for patients to use on their own; it comes in a kit that includes a power supply, a portable battery with charger, a cable, and a carrying case. Patients must keep their heads shaved as they use the system.

The TTFs influences spindle formation and interrupts cell division in cancer cells while sparing normal cells, said Pannullo.

“The cell will pinch off at the point of division during the action of mitosis—during the creation of two daughter tumor cells,” she said. “When this occurs, there is an electrical dipole where the energy essentially is concentrated in this pinched off area of the cell. That results in disruption of the movement of the organelles that are required to divide successfully into the two daughter cells.”

Pivotal Trial Results

In 2011, the FDA’s Center for Devices and Radiological Health approved the NovoTTF-100A System for use in the United States as monotherapy for patients 22 years and older with GBM whose disease recurs after chemotherapy and as an alternative to standard therapy after surgical and radiation options are exhausted.

The National Comprehensive Cancer Network incorporated NovoTTF therapy into its guidelines for central nervous system cancers in 2013, and it is now available at 130 US centers.

The device was approved as a result of the phase III EF-11 study,³ in which 237 patients were randomized to receive either TTF therapy (n = 120) or physician’s choice of chemotherapy (n = 117).

Overall, the median OS was 6.6 months for patients who received TTF therapy versus 6.0 months for individuals who received active chemotherapy.

The response rate was 14% with TTF therapy, including three complete responses, compared with 9.6% with chemotherapy. Among patients in the TTF group, the OS rate was far higher for those who used the device ≥18 hours per day compared with those who used it <18 hours (7.7 months vs 4.5 months; P = .04).

The most prevalent AE associated with TTF therapy was grade 1/2 contact dermatitis, which occurred in 16% of patients who received the treatment. Far fewer AEs were reported with TTF therapy compared with chemotherapy, including gastrointestinal disorders (4% vs 17%), hematologic AEs (3% vs 17%), and infections (4% vs 8%).

Registry Data

While the EF-11 study demonstrated that NovoTTF therapy was comparable to chemotherapy regimens, analyses from the PRiDE registry indicate that the device is producing better results in real-word usage than it did in the pivotal trial, noted Eilon Kirson, MD, PhD, chief science officer and head of Research and Development at Novocure, during the webcast. The registry consists of all patients who were treated with the device in the United States from October 2011 through November 2013. The median duration of treatment was 4.1 months.

Eilon Kirson, MD, PhD

The median OS for patients in the registry was 9.6 months, significantly higher than EF-11 results (HR = 0.56; P = .0003).

Researchers also found that patients who received the therapy after their first recurrence (n = 125) had a median OS of 20 months versus 8.5 months for those who started after a second recurrence, and 4.9 months after the third to fifth recurrence (P <.0001).

Kirson said the device appeals to patients who already have received the standard therapies. “Many of them are searching for something else which won’t harm their quality of life and will allow them to continue to live without the side effects of the more aggressive chemotherapies they may be offered at this stage of their disease,” he said.

References

1. Wong ET, Engelhard HH, Tran DD, et al. NovoTTF-100A alternating electric fields therapy for recurrent glioblastoma: an analysis of patient registry data. J Clin Oncol. 2014;(suppl; abstr e13033).
2. Wong ET, Engelhard HH, Tran DD, et al. Abstract C7: Novo- TTF-100A alternating electric fields therapy for recurrent glioblastoma: an analysis of patient registry data. Presented at: 16th Biennial Canadian Neuro-Oncology Meeting; June 12-14, 2014; Halifax, Canada.
3. Stupp R, Wong ET, Kanner AA, et al. NovoTTF-100A versus physician’s choice chemotherapy in recurrent glioblastoma: a randomised phase III trial of a novel treatment modality [published online May 18, 2012]. Eur J Cancer. 2012;48(4):2192-2202.