Investigating an alternative ring design of transducer arrays for tumor treating fields (TTFields)

Abstract BACKGROUND Tumor Treating Fields (TTFields) use alternating electric fields for the treatment of solid tumors. The therapy is approved for glioblastoma multiforme (GBM), and a phase III trial in 1–10 brain metastases from non-small cell lung cancer (METIS) is currently enrolling patients. In GBM, the layout of the transducer arrays delivering the TTFields to the tumor is optimized for high field intensity in the tumor, while the dose in other regions is decreased. In the setting of secondary brain tumors, as they manifest as brain metastases in 10–30 % of adult cancer patients - especially in melanoma, lung, breast, colon, and kidney cancer - a high TTFields dose in the entire brain would be beneficial. Thus, numerous tumors instead of only one lesion should receive therapeutic TTFields doses. In this study, transducer array layouts aiming for a homogeneous TTFields distribution in the whole brain were investigated. MATERIAL AND METHODS We used computer simulations in a realistic computational head model of a 40+ years old man, constructed in-house from a T1 MRI series, to compute the field distributions obtained with various transducer array layouts. The distribution of TTFields delivered by pairs of transducer arrays at different positions on the head and neck was simulated using Sim4Life v3.0 (ZMT Zürich). For each layout, we determined and compared the mean and median field intensities in five pre-determined sections of the brain: (1) the cerebellum and brain stem together with other infra-tentorial anatomical regions; and (2–5) the four cerebral quadrants. RESULTS One array layout could be identified yielding median intensities between 1.5 V/cm to 1.7 V/cm in all areas and a homogeneous distribution within the brain. This layout is composed of one pair of arrays positioned on the right temple and left scapula, and the other pair positioned on the left temple and right scapula. CONCLUSION This study was able to determine a novel TTFields transducer array layout that might be used for treatment of the entire brain with therapeutic intensities, as would be beneficial in patients with brain metastases.

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EXTH-37. A NOVEL TRANSDUCER ARRAY LAYOUT FOR DELIVERING TUMOR TREATING FIELDS TO THE SPINE

Neuro-Oncology ◽

10.1093/neuonc/noz175.369 ◽

2019 ◽

Vol 21 (Supplement_6) ◽

pp. vi90-vi90

Author(s):

Ariel Naveh ◽

Ofir Yesharim ◽

Ze’ev Bomzon

Keyword(s):

Spinal Cord ◽

Electric Fields ◽

Computational Models ◽

Leptomeningeal Disease ◽

Computational Simulations ◽

Transducer Array ◽

Tumor Treating Fields ◽

Transducer Arrays ◽

Perpendicular Field ◽

Computational Platform

Abstract Tumor Treating Fields (TTFields) are an antimitotic technology utilising electric fields to disrupt mitosis in cancer cells. TTFields are currently approved by the FDA for the treatment of Glioblastoma Multiforme (GBM) and Malignant Pleural Mesothelioma (MPM). TTFields are delivered through 2 pairs of transducer arrays placed on the patient’s skin. Each pair delivers TTFields in a single direction, and the pairs are placed to provide perpendicular field. Preclinical studies show that 1V/cm is the clinical threshold for the treatment to be effective. Some types of cancers send metastases to the spinal cord and CSF, i.e. leptomeningeal disease. The purpose of this study was to find transducer array layouts that deliver TTFields to the spine at therapeutic intensities of above 1 V/cm. Computational simulations testing the delivery of TTFields to the spine were performed using the Sim4Life 4.0 (ZMT Zurich) computational platform, and the Duke 3.1 and Ella 3.0 (ITI’S, Zurich) realistic computational models of a male and female respectively. “Standard” layouts in which a pair of arrays are placed on the front and back of the patient and second pair on the lateral aspects of the patient failed to deliver TTFields at therapeutic intensities to the spinal cord. This is probably because the spinal cord is surrounded by the CSF and spine, which shunt the electric fields from reaching the spinal cord. However, field intensities above 1 V/cm were observed when delivering TTFields when both arrays were placed on the patients back, with a first array placed close to the neck, and second array placed towards the thighs. In this case, the spinal cord and surrounding CSF act as a conductive cable, directing the electric field along the spine. This novel layout opens the possibility for treating cancerous disease along the spine.

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

Neuro-Oncology ◽

10.1093/neuonc/nov231.07 ◽

2015 ◽

Vol 17 (suppl 5) ◽

pp. v196.3-v196

Author(s):

Mijal Munster ◽

Shay Cahal ◽

Roni Blatt ◽

Moshe Giladi ◽

Aviran Itzhaki ◽

...

Keyword(s):

Tumor Treating Fields ◽

Transducer Arrays ◽

Ceramic Transducer

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RBIO-01. DEVELOPING THE FRAMEWORK FOR TUMOR TREATING FIELDS (TTFIELDS) TREATMENT PLANNING FOR A PATIENT WITH ASTROCYTOMA IN THE SPINAL CORD

Neuro-Oncology ◽

10.1093/neuonc/noab196.758 ◽

2021 ◽

Vol 23 (Supplement_6) ◽

pp. vi191-vi191

Author(s):

Jennifer de Los Santos ◽

Smadar Arvatz ◽

Oshrit Zeevi ◽

Shay Levi ◽

Noa Urman ◽

...

Keyword(s):

Spinal Cord ◽

Treatment Planning ◽

Spinal Tumor ◽

Specific Model ◽

Patient Specific ◽

Transducer Array ◽

Tumor Bed ◽

Tumor Treating Fields ◽

Transducer Arrays ◽

Healthy Female

Abstract The use of Tumor Treating Fields (TTFields) following resection and chemoradiation has increased survival in patients with Glioblastoma. Patient-specific planning for TTFields transducer array placement has been demonstrated to maximize TTFields dose at the tumor: providing higher TTFields intensity (≥ 1.0 V/cm) and power density (≥ 1.1 mW/cm3) which are associated with improved overall survival. Treatment planning was performed for a 48 year old patient following T10-L1 laminectomy, gross total resection, and postoperative chemoradiation for an anaplastic astrocytoma of the spinal cord. An MRI at 3 weeks following chemoradiation showed tumor recurrence. Based on the post-chemoradiation MRI, a patient-specific model was created. The model was created by modifying a realistic computational phantom of a healthy female. To mimic the laminectomy, the lamina in T10-L1 was removed, and the region assigned electric conductivity similar to that of muscle. A virtual mass was introduced into the spinal cord. Virtual transducer arrays were placed on the model at multiple positions, and delivery of TTFields simulated. The dose delivered by different transducer array layouts was calculated, and the layouts that yielded maximal dose to the tumor and spine identified. Transducer array layouts, in which the arrays were placed on the back of the patient with one array above the tumor and one array below the tumor, yielded the highest doses at the tumor site. Such layouts yielded TTFields doses of over 3.4mW/cm3 which is well above the threshold dose of 1.1 mW/cm3 reported previously [Ballo et al. Red Jour 2019]. The framework developed for TTFields dosimetry and treatment planning for this spinal tumor will have the potential to increase dose delivery to the tumor bed while optimizing placement that may enhance comfort and encourage device usage.

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