RTRB-07: PRECLINICAL EVALUATION OF IRRADIATION THROUGH TUMOR TREATING FIELDS (TTFIELDS) CERAMIC TRANSDUCER ARRAYS

TTFields are an effective anticancer modality delivered via continuous, noninvasive application of low intensity, intermediate frequency, alternating electric fields. TTFields are delivered using insulated ceramic transducer arrays that are placed directly on the scalp in the region surrounding a tumor. Preclinical data suggest that the combination of TTFields with irradiation is most effective when TTFields are applied immediately after exposure to irradiation therapy. In practice, this could be accomplished by leaving the transducer arrays attached to the patients' skin during radiation therapy. Initial investigations using an ion chamber connected to a unidos dosemeter demonstrated that the TTFields transducer arrays absorb only a small fraction of the irradiation energy but lead to a dramatic increase in the energy directly below the ceramic arrays. This could potentially abolish the "skin sparing" effect. The purpose of this study was to evaluate the impact of direct irradiation through the TTFields ceramic transducer arrays on rat skin. Insulated ceramic transducers with hydrogel identical to those used for TTFields application in glioblastoma patients were placed on a rat's head. No additional skin adverse events were observed when single irradiation doses of 2-15 Gy were applied to the rat head through the transducers. In order to further test potential skin damage in conditions similar to clinical practice, rats were irradiated with 2 Gy, five times a week for two weeks through ceramic arrays placed on the rat's dorsal skin. Skin screening revealed that irradiation through the ceramic arrays did not lead to adverse skin reactions. These results should be further validated through clinical testings.