P01.077 Optimizing array layouts for glioblastoma therapy with tumor treating fields (TTFields) - Use of oblique array layouts surpass default left-right/anterior-posterior positions in a computer simulation model

Abstract Background Tumor treating fields (TTFields, Optune®) is an effective treatment for glioblastoma. The antimitotic effects of TTFields are induced by low-intensity, intermediate frequency (200 kHz) alternating electric fields, delivered through two pairs of transducer arrays placed on the patient’s scalp. The present study aimed to identify optimal array positions that induced the highest electric field in the tumor by analyzing systematic variations in array layouts. Material and Methods TTFields distribution was computed using finite element methods with a realistic computational head model. A standard anterior-posterior (AP) layout was rotated in 15-degree intervals in the same plane around a central cranio-caudal axis of the head to investigate thirteen array positions. During subdivision, tumors were placed at nineteen different frontoparietal positions in the array rotation plane. Results TTFields distribution was affected by different array layouts. Two array layouts were identified to be suitable for most tumors. These identified positions led to TTFields intensities that were approximately 30–40% higher in the tumors than in standard AP and left/right (LR) layouts. The two optimal layouts were oriented at 90-degree intervals to each other. Subsequent analysis of combining two array pairs revealed a single optimum layout. For each tumor position, only one optimum layout combination was identified, which was usually oriented in 15–45 degree angles relative to the sagittal plane. In each case, an oblique layout that was orientated at 45 degrees to the sagittal plane was effective for most tumor localizations and superior to the default AP/LR layout combination. Determining factors for layout optimization were high field intensities at transducers located on the edges of the arrays, with high fields close to the peripheral transducers. Conclusion The present study provides guiding principles for optimal TTFields layout design and planning. Individual patient-specific models should be used to determine TTFields distributions more accurately.