Abstract 5497: Transducer array layouts for treating head and neck cancer with TTFields
Authors: Bomzon Ze'ev , Naveh Ariel , Abraham Yissachar 
Published: September 2020

Abstract
Tumor Treating Fields (TTFields) are a novel antimitotic treatment for solid tumors. TTFields utilize low frequency (1-4 V/cm) electric fields in the intermediate frequency range (100-300 kHz), and are currently FDA approved for the treatment of glioblastoma multiforme (GBM) using the Optune device. TTFields are also approved for multi pleural mesothelioma (MPM). The fields are delivered using two pairs of transducer arrays placed on different places on the patient's skin. In order for the treatment to be efficacious, placement should be performed in a manner such that the tumor receives significant dose of TTFields. An effective dose is considered to be at least 1 V/cm in the region of interest. Nevertheless, preclinical studies has shown that higher field values result in greater tumor growth inhibition. When TTFields are delivered, the field distribution is determined by a series of non-intuitive factors, such as the different electric conductivity of the different organs, making intuitive placement inaccurate. Therefore, different parts of the body require specific array layout design. Such case occurs with head and neck cancer. In this work we examined our ability to deliver TTFields to the larynx and its surroundings. Methods We used computer simulations to estimate the field distribution different layouts would provide. The simulations used a computational phantom representing a 34 years old male (DUKE 3.1, ITI'S foundation, Zurich). We placed virtual transducer arrays comprising either 13 or 9 ceramic disks were placed on the model's skin and delivery of TTFields to the model was simulated Sim4Life v4.4 (by ZMT, Zurich). 6 different array layouts were tested. In layouts 1-3, one array comprising 13-disks was placed on the model's scalp while the other 13-disks array was placed on its chest. Forcase 4 a pair of 9-disks arrays was used, one array was placed on the forehead of the model and the other on it'supper chest. In cases 5-6, we placed 9-disks arrays around the patient's neck. We then analyzed the field intensity within a region of interest (ROI) including the larynx and surrounding tissues. Results In cases 1-2 and 4, mean field intensities within the ROI were 3.29 V/cm, 3.46 V/cm and 2.6 V/cm, respectively, well above the clinical threshold of 1 V/cm. Cases 3, 5 and 6 showed to have median field of 1.41, 1.37 and 1.27 V/cm. Though still above the clinical threshold, these field intensities are significantly lower than in the other cases. This, apparently, is due to current flow through the neck muscles behind the ROI. Conclusions This study shows that it is possible to deliver TTFields at therapeutic intensities to the larynx and the surrounding tissues. Thus, TTFields may be a therapeutic option for treating head and neck tumors located in the larynx and the surrounding tissues.
Citation Format: Ze'ev Bomzon, Ariel Naveh, Yissachar Abraham. Transducer array layouts for treating head and neck cancer with TTFields [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5497.