Compatibility of Topical Products to Manage Skin Irritation Associated with TTFields.

Abstract

Tumor Treating Fields (TTFields) are electric fields that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields therapy is approved for the treatment of recurrent glioblastoma (GBM), newly diagnosed GBM, and pleural mesothelioma, and is currently under clinical investigations for the treatment of other types of cancers. TTFields therapy is delivered continuously and non-invasively, using a portable signal generator connected to 4 arrays attached to the skin. Treatment of at least 18 hours per day is recommended for increasing effectiveness. The main treatment-related adverse effect reported in clinical trials and post-marketing surveillance studies has been low-grade skin irritation under the arrays, which may be treated in most cases with the use of topical steroids or intermittent treatment interruptions. However, for maintaining treatment effectiveness, skin care products suitable for use under the TTFields arrays are those that do not affect field currents. The goal of this study was to investigate strategies to alleviate skin irritation without compromising treatment effectiveness. TTFields (200 kHz) were applied to rats (Sprague Dawley, 10-20 weeks of age, body weight over 250 gr) using ceramic disks and hydrogels identical to those used with human arrays. The rat torso was depilated, and TTFields were applied to the rat torso before and after applying various skin care products to the surface beneath the arrays. After reaching a steady state, average currents were extracted from the device's log files. Percent change in current was calculated from the measurements with and without the product. Tested products could be divided into groups according to their medical use: antibiotics, antiseptics, cleansers/adhesive removers, skin barriers, moisturizers, topical corticosteroids, and antiperspirants. The products could also be categorized by their type: creams, gels, soaps, sprays, ointments, wipes/pads, foams, and lotions. Skin care products that significantly reduced currents were mainly ointments. Typical ingredients of ointments are mineral oil and petrolatum, which are expected to create a hydrophobic layer, thereby reducing ionic conduction and hence field currents. These ingredients also hinder adherence of the acrylic-based tape to the skin thus compromising mechanical fixation of the arrays, leading to poor connectivity and hence reduced currents. Identification of products for treating skin irritation that are compatible with TTFields therapy is important for improving patient's quality of life and increasing device usage. Skin care products containing petrolatum should not be applied under the arrays to avoid compromising treatment effectiveness.