Alternating electric fields (TTFields) in combination with paclitaxel are therapeutically effective against ovarian cancer cells in vitro and in vivo.

Long-term survival rates for advanced ovarian cancer patients have not changed appreciably over the past four decades; therefore, development of new, effective treatment modalities remains a high priority. Tumor Treating Fields (TTFields), a clinically active anticancer modality utilize low-intensity, intermediate frequency, alternating electric fields. The goal of this study was to evaluate the efficacy of combining TTFields with paclitaxel against ovarian cancer cells in vitro and in vivo. In vitro application of TTFields on human ovarian cancer cell lines led to a significant reduction in cell counts as compared to untreated cells. The effect was found to be frequency and intensity dependent. Further reduction in the number of viable cells was achieved when TTFields treatment was combined with paclitaxel. The in vivo effect of the combined treatment was tested in mice orthotopically implanted with MOSE-LTICv cells. In this model, combined treatment led to a significant reduction in tumor luminescence and in tumor weight as compared to untreated mice. The feasibility of effective local delivery of TTFields to the human abdomen was examined using finite element mesh simulations performed using the Sim4life software. These simulations demonstrated that electric fields intensities inside and in the vicinity of the ovaries of a realistic human computational phantom are about 1 and 2 V/cm pk-pk, respectively, which is within the range of intensities required for TTFields effect. These results suggest that prospective clinical investigation of the combination of TTFields and paclitaxel is warranted.

The Impact of Tumor Treating Fields on Glioblastoma Progression Patterns.

PURPOSE: Tumor-treating fields (TTFields) are an antimitotic treatment modality that interfere with glioblastoma (GBM) cell division and organelle assembly by delivering low-intensity, alternating electric fields to the tumor. A previous analysis from the pivotal EF-14 trial demonstrated a clear correlation between TTFields dose density at the tumor bed and survival in patients treated with TTFields. This study tests the hypothesis that the antimitotic effects of TTFields result in measurable changes in the location and patterns of progression of newly diagnosed GBM. METHODS AND MATERIALS: Magnetic resonance images of 428 newly diagnosed GBM patients who participated in the pivotal EF-14 trial were reviewed, and the rates at which distant progression occurred in the TTFields treatment and control arm were compared. Realistic head models of 252 TTFields-treated patients were created, and TTFields intensity distributions were calculated using a finite element method. The TTFields dose was calculated within regions of the tumor bed and normal brain, and its relationship with progression was determined. RESULTS: Distant progression was frequently observed in the TTFields-treated arm, and distant lesions in the TTFields-treated arm appeared at greater distances from the primary lesion than in the control arm. Distant progression correlated with improved clinical outcome in the TTFields patients, with no such correlation observed in the controls. Areas of normal brain that remained normal were exposed to higher TTFields doses compared with normal brain that subsequently exhibited neoplastic progression. Additionally, the average dose to areas of the enhancing tumor that returned to normal was significantly higher than in the areas of the normal brain that progressed to enhancing tumor. CONCLUSIONS: There was a direct correlation between TTFields dose distribution and tumor response, confirming the therapeutic activity of TTFields and the rationale for optimizing array placement to maximize the TTFields dose in areas at highest risk of progression, as well as array layout adaptation after progression.

The dielectric properties of skin and their influence on the delivery of tumor treating fields to the torso: a study combining in vivo measurements with numerical simulations.

The study of the dielectric properties of tissues plays a key role in understanding the interaction between electromagnetic energy and the human body, for safety assessments of human exposure to electromagnetic fields, as well as for numerous biomedical applications such as tumor treating fields (TTFields). TTFields are low-intensity alternating electric fields in the 100-500 kHz frequency range, which have an antimitotic effect on cancerous cells. TTFields are delivered to the body through pairs of transducer arrays placed on a patient's skin in close proximity to the tumor. Therefore, it is essential to understand how the skin's dielectric properties affect TTFields delivery in clinical settings. In this paper, we present a study combining in vivo measurements with numerical simulations that elucidate how different layers of the skin influence TTFields distribution in the body. The dielectric properties of the skin were measured on volunteers using a setup that ensured skin conditions resembled those when TTFields are delivered to patients. The measured properties were incorporated into a realistic human computational phantom and delivery of TTFields to the phantom's abdomen was simulated. The total impedance of the simulated model was within the mid-range of impedance values measured in patients with pancreatic cancer treated with TTFields. A computational study investigating model sensitivity to the dielectric properties of the skin and subcutaneous adipose tissue (SAT) showed that when skin conductivity increased above a threshold value, the total impedance of the model was largely insensitive to changes in the conductivity of these tissues. Furthermore, for a given current, the field intensity within the internal organs was mostly unaffected by skin properties but was highly sensitive to the conductivity of the organ itself. This study provides a new insight into the role of skin in determining the distribution of TTFields within the body.

Correlation of Tumor Treating Fields Dosimetry to Survival Outcomes in Newly Diagnosed Glioblastoma: A Large-Scale Numerical Simulation-Based Analysis of Data from the Phase 3 EF-14 Randomized Trial.

INTRODUCTION: Tumor Treating Fields (TTFields) are approved for glioblastoma based on improved overall survival (OS) and progression-free survival (PFS) in the phase 3 EF-14 trial of newly diagnosed glioblastoma. To test the hypothesis that increasing TTFields dose at the tumor site improves patient outcomes, we performed a simulation-based study investigating the association between TTFields dose and survival (OS and PFS) in patients treated with TTFields in EF-14. METHODS AND MATERIALS: EF-14 patient cases (N = 340) were included. Realistic head models were derived from T1-contrast images captured at baseline. The transducer array layout on each patient was obtained from EF-14 records; average compliance (fraction of time patient was on active treatment) and average electrical current delivered to the patient were derived from log files of the TTFields devices used by patients. TTFields intensity distributions and power densities were calculated using the finite element method. Local minimum dose density (LMiDD) was defined as the product of TTFields intensity, tissue-specific conductivities, and patient compliance. The average LMiDD within a tumor bed comprising the gross tumor volume and the 3-mm-wide peritumoral boundary zone was calculated. RESULTS: The median OS and PFS were significantly longer when the average LMiDD in the tumor bed was ≥0.77 mW/cm3: OS was 25.2 versus 20.4 months (P = .003, hazard ratio [HR] = 0.611) and PFS was 8.5 versus 6.7 months (P = .02, HR = 0.699). The median OS and PFS were longer when the average TTFields intensity was >1.06 V/cm: OS was 24.3 versus 21.6 months (P = .03, HR = 0.705) and PFS was 8.1 versus 7.9 months (P = .03, HR = 0.721). CONCLUSIONS: In this study we present the first reported analysis demonstrating patient-level dose responses to TTFields. We provide a rigorous definition for TTFields dose and set a conceptual framework for future work on TTFields dosimetry and treatment planning.

First steps to creating a platform for high throughput simulation of TTFields.

Tumor Treating Fields (TTFields) are low intensity alternating electric fields in the 100-500 KHz frequency range that are known to have an anti-mitotic effect on cancerous cells. In the USA, TTFields are approved by the Food and Drug Administration (FDA) for the treatment of glioblastoma (GBM) in both the newly diagnosed and recurrent settings. Optimizing treatment with TTFields requires a deep understanding of how TTFields distribute within the brain. To address this issue, simulations using realistic head models have been performed. However, the preparation of such models is time-consuming and requires a high level of expertise, limiting the usefulness of these models for systematic studies in which the testing of multiple cases is required. Here we present a platform for rapidly simulating TTFields distributions in multiple scenarios. This platform enables high throughput computational simulations to be performed, allowing comparison of field distributions within the head in multiple clinically relevant scenarios. The simulation setup is simple and intuitive, allowing non-expert users to run simulations and evaluate results, thereby providing a valuable tool for studying how to optimize TTFields delivery in the clinic.

Using computational phantoms to improve delivery of Tumor Treating Fields (TTFields) to patients.

This paper reviews the state-of-the-art in simulation-based studies of Tumor Treating Fields (TTFields) and highlights major aspects of TTFields in which simulation-based studies could affect clinical outcomes. A major challenge is how to simulate multiple scenarios rapidly for TTFields delivery. Overcoming this challenge will enable a better understanding of how TTFields distribution is correlated with disease progression, leading to better transducer array designs and field optimization procedures, ultimately improving patient outcomes.

Mitotic Spindle Disruption by Alternating Electric Fields Leads to Improper Chromosome Segregation and Mitotic Catastrophe in Cancer Cells.

Tumor Treating Fields (TTFields) are low intensity, intermediate frequency, alternating electric fields. TTFields are a unique anti-mitotic treatment modality delivered in a continuous, noninvasive manner to the region of a tumor. It was previously postulated that by exerting directional forces on highly polar intracellular elements during mitosis, TTFields could disrupt the normal assembly of spindle microtubules. However there is limited evidence directly linking TTFields to an effect on microtubules. Here we report that TTFields decrease the ratio between polymerized and total tubulin, and prevent proper mitotic spindle assembly. The aberrant mitotic events induced by TTFields lead to abnormal chromosome segregation, cellular multinucleation, and caspase dependent apoptosis of daughter cells. The effect of TTFields on cell viability and clonogenic survival substantially depends upon the cell division rate. We show that by extending the duration of exposure to TTFields, slowly dividing cells can be affected to a similar extent as rapidly dividing cells.