Alternating Tumor Treating Fields (TTFields) Layouts for Reduced Risk of Skin Irritation during Treatment of Solid Tumors in the Epigastric Region

Abstract

Tumor Treating Fields (TTFields) therapy is a noninvasive, locoregional treatment modality that physically disrupts cancer cell processes needed for cancer cell viability and tumor progression. TTFields are electric fields that are delivered noninvasively to the designated tumor site via a portable medical device using 2 pairs of skin-placed transducer arrays. To minimize the risk of skin irritation, arrays are replaced every few days. TTFields treatment planning guidelines (baseline plans) are utilized to optimize the field intensity delivered to target tumor regions for several indications under investigation, e.g., pancreatic cancer. We propose a novel schema of 'Alternating TTFields Layouts' (ATLs) to extend skin recovery time; whereby 2 non-overlapping array layouts are used in alternating sequence every few days. ATLs vary according to tumor location, anatomy, sex, and body mass index to deliver comparable field intensities to baseline plans. To estimate the electric field distributions generated by various ATLs, 3 computational human models were utilized: (1) a male (DUKE), (2) a female (ELLA), and (3) an obese male (FATS) (IT'IS Foundation, Zürich). Simulations of electric field distributions were performed using Sim4Life v6.2 (ZMT, Zürich). TTFields delivery to the epigastric region was simulated using pairs of array layouts positioned at different locations on the skin in the thoracic and abdominal regions. For each model, we analyzed abdominal cavity tissue within the epigastric region to calculate and compare the local average field intensity (LAFI) and local minimum power density (LMiPD) for each ATL relative to the model's baseline layout. Each model yielded a LAFI of >1 V/cm in the epigastric region for all ATLs. For the DUKE, ELLA, and FATS models the LAFI values were higher by 3%, 6% and 4%, respectively, for ATL-1 and similar (0-1%) for ATL-2 vs. the baseline layouts of each model. Compared to the baseline layouts, LMiPD values of ATL-1 and ATL-2, respectively, were higher by 1% and 11% for DUKE, 13% and 4% for ELLA, and 20% and 14% for FATS. Using ATLs, we present a novel treatment plan for TTFields therapy within the epigastric region. This new treatment plan is designed to extend skin recovery time in an effort to prevent or minimize the risk of skin irritation and to increase TTFields usage, which correlates with extended survival, and potentially improve overall patient experience. Plans for a clinical evaluation of the proposed schema and its applicability to other types of cancer and to other regions in the thorax and abdomen are currently underway.