Abstract 1569: Optimizing transducer array configuration for treatment of pancreatic cancer using Tumor Treating Fields (TTFields)
Authors: Naveh Ariel , Bomzon Ze'ev , Urman Noa , Yesharim Ofir , Kirson Eilon D. , Weinberg Uri 
Published: July 2017

Abstract
Introduction
TTFields is an antimitotic cancer treatment that utilizes low intensity (1-3 V/cm) alternating electric fields in the intermediate frequency (100-300 kHz) that are delivered in two orthogonal directions using 2 pairs of transducer arrays. TTFields are currently approved for Glioblastoma Multiforme (GBM). A phase II clinical trial (EF-20) showed that TTFields in combination with gemcitabine was safe in patients with locally advanced pancreatic cancer.
Preclinical studies show that the effect of TTFields is intensity-dependent with a therapeutic threshold of 1 V/cm. Simulation-based studies show that the field distribution changes with array placement. Treatment planning with arrays positioned on the scalp to maximize field intensity to the tumor is standard of practice when treating GBM. Studies to examine array layout on the abdomen to maximize the field distribution in this region have not been done. In the EF-20 study, a generic layout was used. We used computer simulations to test how altering the transducer array layout on the mid-body alters the field distribution within the abdomen and pancreas.
Methods
To simulate delivery of TTFields to the abdomen, we used a realistic computerized model of a human male (DUKE 3.0 from ZMT-Zurich). Eight different layouts utilizing combinations of arrays with either 13 or 20 disks placed at different locations on the abdomen were simulated. In order to generate TTFields, an alternating voltage difference with a peak to peak magnitude of 100V and a frequency of 150 KHz was imposed on the outer surfaces of the disks of each pair of arrays. The simulations were performed using ZMT's Sim4Life V3.0 electro-quasi-static solver. For each pair of transducer arrays, the mean field intensity in the abdomen and chest, and in the pancreas and liver, was calculated.
Results
All eight layouts delivered fields with mean intensities of about 2 V/cm to the abdomen. The average field intensity delivered to the pancreas and the liver exceeded the therapeutic threshold of 1 V/cm for all layouts. The highest intensities were delivered to the pancreas by layouts in which a 20-disk array was placed at the middle of the back, and either a 20 disk array placed at the middle of the abdomen or a 13 disk array placed on the front-left side of the abdomen over the pancreas. Generally, field intensities in the pancreas are lower than in the rest of the abdomen because of the high electric conductivity of this organ.
Conclusion
This work shows that TTFields can be delivered to the pancreas with intensities well above the therapeutic threshold of 1 V/cm, and that altering the location of the arrays on the abdomen can influence the field intensity and distribution within the body. This work forms the basis for developing optimal strategies for delivering TTFields to the pancreas.
Citation Format: Ariel Naveh, Ze'ev Bomzon, Noa Urman, Ofir Yesharim, Eilon D. Kirson, Uri Weinberg. Optimizing transducer array configuration for treatment of pancreatic cancer using Tumor Treating Fields (TTFields) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1569. doi:10.1158/1538-7445.AM2017-1569