MODL-13. Sensitivity of Tumor Treating Fields (TTFields) treatment planning to healthy tissue segmentation inaccuracies

Abstract

Abstract TTFields are FDA approved for treating patients with GBM. TTFields utilize low intensity electric fields with intermediate frequency (100-500 kHz) that disrupt cellular processes critical for cancer cell viability and tumor progression. TTFields have been shown to disrupt multiple phases of the cell cycle including metaphase, anaphase, and telophase, resulting in cellular apoptosis. TTFields are administered through two pairs of capacitive arrays placed on the patient’s scalp. As TTFields are a dose dependent therapy, optimization of array layout for maximizing field intensity may improve survival rates of patients. Thus, Novocure is developing a treatment planning system, in which MR images are used to create a patient-specific model, which in turn is used for simulating electric fields distribution. However, the segmentation process of the MRIs is prone to errors that may influence the choice of array layout, and consequently provide lower TTFields dose than possible. To test the sensitivity of layout chosen to such inaccuracies, we placed different array layouts on the highly detailed MIDA head model and simulated the resulting LMiPD from each configuration. We then simplified the model in several phases and compared the resulting array layout ranking between the full model and each simplified model. Our results show that though the calculated LMiPD is very sensitive to the quality of the model, the ranking pattern between the detailed and simplified models is similar. Some alterations do occur, but this mostly happens when the LMiPD values between switched layouts are very close, rendering these alterations clinically insignificant. Based on these results, we conclude that the ranking order of array layouts by LMiPD dose does not significantly change between detailed and simplified head models even though the LMiPD dose itself is sensitive to the quality of the head model.