Tumor-treating Fields Research Articles

Glioma diagnosis and therapy: Current challenges and nanomaterial-based solutions.

Glioma is often referred to as one of the most dreadful central nervous system (CNS)-specific tumors with rapidly-proliferating cancerous glial cells, accounting for nearly half of the brain tumors at an annual incidence rate of 30-80 per a million population. Although glioma treatment remains a significant challenge for researchers and clinicians, the rapid development of nanomedicine provides tremendous opportunities for long-term glioma therapy. However, several obstacles impede the development of novel therapeutics, such as the very tight blood-brain barrier (BBB), undesirable hypoxia, and complex tumor microenvironment (TME). Several efforts have been dedicated to exploring various nanoformulations for improving BBB permeation and precise tumor ablation to address these challenges. Initially, this article briefly introduces glioma classification and various pathogenic factors. Further, currently available therapeutic approaches are illustrated in detail, including traditional chemotherapy, radiotherapy, and surgical practices. Then, different innovative treatment strategies, such as tumor-treating fields, gene therapy, immunotherapy, and phototherapy, are emphasized. In conclusion, we summarize the article with interesting perspectives, providing suggestions for future glioma diagnosis and therapy improvement.

Abstract IA010: Meeting the challenge of pancreatic cancer

Abstract Approximately one third of patients (pts) with pancreatic adenocarcinoma (PDA) present with locally advanced unresectable disease (LAPC). Majority of pts with LAPC have micrometastatic disease at presentation. However, median survival times exceed those of pts with radiologically visible metastases and is currently around 14-16 months (versus less than 1 year). Initial treatment strategies in LAPC focused on radiation that did not improve survival. With improvements in systemic therapies, current treatments of LAPC are based on cytotoxic combinations similar to ones used in metastatic PDA. However, benefits of cytotoxic therapy remain very modest. Unfortunately, the development of systemic therapy for PDA was plagued by repeated failures of randomized clinical trials of a range of targeted and other agents. In recent years, we exponentially advanced knowledge of PDA’s molecular biology and are attempting to learn from our clinical failures. One thing that stood out, with very few exceptions, is lack of success in single target/pathway strategies, especially in the absence of predictive biomarkers and lack of targetable “driver” mutations. Immune checkpoint inhibitors were ineffective unlike successes in other cancers. Focus has therefore shifted to rational strategies based on biology that defines phenotype along with ongoing attempts to refine molecular characterizations of PDA. Major research strategies include targeting the stroma to enhance drug delivery (e.g., CEND-1), reversing the immune suppressive microenvironment (combinatorial immunotherapy), exploiting DNA repair defects (e.g., BRCA mutations), and most importantly tackling KRAS oncogene. KRASG12C, KRASwt, BRCAmutated, and microsatellite instability provide additional treatment opportunities in up to 10% of PDA patients. The goal of new therapy developments in LAPC must address the locoregional morbidity of the primary tumor with the ultimate goal of prolonging survival. Examples of ongoing research in locoregionally directed therapy include ablative radiation and tumor treating fields (TTF) that attempt to control its growth, reduce the tumor bulk, and improve possibilities of tumor resection. As our systemic therapies improve, locoregional therapy becomes more relevant. Improvements in molecular classifications of PDA, refinements in the use of organoids to predict drug and radiation effect, and use of liquid biopsies are examples of measures that will provide foundations for personalized treatment approaches. Collectively, we have endless opportunities for translational research based on advances in PDA’s basic science and our experiences from the many “negative” clinical trials. Citation Format: Philip A. Philip. Meeting the challenge of pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr IA010.

EXTH-05. TOWARD 100% CLINICAL EFFICACY FOR TUMOR-TREATING FIELDS

Abstract In vitro and in animal models of various tumor cell types, empirical data suggest tumor-treating fields (TTFields) can attain 100% efficacy, with two pre-conditions: 1) Delivering sufficient electric field strength to the target tumor cells, and 2) Changing the direction of the imposed electric field such that intra-cellular structures at any angle with respect to the field see the required efficacious field strength. Requirement #2 reflects empirical findings as well as prevailing theories of TTFields’ mechanism of action, which center on mitosis disruption via energy imparted to polarizable intracellular structures aligned with the field. We tried various trial curve-fits to TTFields empirical dose-response curves. Quadratic formulae yield a close fit, resembling well-known radiotherapy linear-quadratic (LQ) curves and suggesting a connection between the mechanisms of the two treatment modalities: F98 (rat glioma): -16.3271x2 - 0.664019x+100 (R2=0.9995); MDA-MB-231 (human breast cancer): -9.64922x2 + 2.96348x + 100 (R2=0.9999); H1299 (human non-small cell lung carcinoma): -12.0515x2 - 1.58272x + 100 (R2=0.9993); B16 (mouse melanoma): -83.8066x2 + 47.4537x + 100 (R2=0.9954). We extrapolate these fits to predict the approximate required field strength seen at the target cells for 100% efficacy: F98: 2.45 V/cm; MDA-MB-231: 3.4 V/cm; H1299: 2.8 V/cm; B16: 1.4 V/cm. Alternatively, the LQ fits may not reflect the extrapolated high amplitude range for which data is lacking. Under two assumptions, 1) intracellular structures are randomly oriented in vivo, and 2) only two changes of TTFields direction are used, as is the current clinical practice, then extrapolating the dose-response curves predicts that infinite field strength is required for 100% efficacy, since some intracellular structures must be oriented at 90 degrees to the imposed field and the cosine of 90 degrees is zero. Adding a third TTFields direction, not necessarily orthogonal to the plane of the other two directions, can solve this problem.

A Propensity-Matched Study to Evaluate PTEN and TP53 Mutations as Predictive Biomarkers of Survival in Newly Diagnosed IDH-Wildtype Glioblastoma after Tumor Treating Fields

<h3>Purpose/Objective(s)</h3> The addition of tumor treating fields (TTF) to adjuvant temozolomide (TMZ) for newly diagnosed glioblastoma (GBM) has been shown to improve overall survival (OS) and progression-free survival (PFS). PTEN and TP53 mutations have been shown to increase response to TTF in recurrent GBM and preclinical GBM models, respectively. However, no effect modification has been shown for these makers in newly diagnosed GBM patients. This study aims to leverage a large, multi-institutional cohort to evaluate whether PTEN or TP53 mutation can predict survival in newly diagnosed GBM patients receiving adjuvant TTF. <h3>Materials/Methods</h3> Histologically-confirmed, supratentorial, and nonmetastatic IDH-wildtype GBM patients aged ≥ 18 yrs with KPS ≥ 60 who received chemoradiation and adjuvant TMZ ± TTF at 3 cancer centers were retrospectively reviewed. RT included long and short-course regimens. TTF patients were compared to patients without TTF using 1:1 propensity-score matching (PSM) based on age, sex, MGMT promotor methylation status, KPS, extent of resection, and RT course. PTEN and TP53 status were assessed using next generation sequencing of tumor specimens. Interaction of PTEN or TP53 with TTF for OS and PFS was evaluated using Cox regression and are presented as hazard ratios (HR) with 95% confidence intervals. Median OS (months) was calculated using the Kaplan Meier method. <h3>Results</h3> From 10/2015 to 1/2021, 245 patients met inclusion criteria, including 87 (36%) who received adjuvant TTF. After PSM (n = 174), no significant difference in any covariate was noted between TTF and no TTF arms with standardized mean differences < 0.2 signifying a good match. The cohort had 40% PTENmutant and 25% TP53mutant cases. Neither TTF use nor PTEN or TP53 mutation were significantly associated with OS or PFS. There was also no significant interaction of PTEN or TP53 with TTF for OS or PFS (Table 1). Among PTENmutant cases, TTF use resulted in similar OS (21.5 months [95% CI: 17.0 – 26.0]) compared to chemoradiotherapy without TTF (20.5 months [95% CI: 15.1 – 26.0]). Among TP53mutant cases, TTF use was also associated with similar OS (24.7 months [95% CI: 15.9 - 33.4]) compared to chemoradiotherapy without TTF (17.9 months [95% CI: 12.6 – 23.1]). <h3>Conclusion</h3> In this propensity-matched study, PTEN and TP53 mutations were not predictive of survival for GBM patients receiving adjuvant TTF. However, adjuvant TTF was also not associated with improved survival, which may be due to unaccounted selection bias or TTF device compliance.

Chemoradiation Treatment with or without Concurrent Tumor-Treating Fields (TTFields) in Patients with Newly Diagnosed Glioblastoma (GBM)

<h3>Purpose/Objective(s)</h3> The standard of care for newly diagnosed glioblastoma (GBM) after maximal safe resection or biopsy includes concurrent temozolomide (TMZ) and radiation therapy (RT) followed by adjuvant Tumor Treating Fields (TTF) and maintenance TMZ. Preclinical studies suggest TTF and radiotherapy work synergistically. We evaluate the clinical benefit of concurrent TTF with CRT vs adjuvant TTF with TMZ after CRT. <h3>Materials/Methods</h3> Concurrent TTF with CRT patients were enrolled in a single-arm pilot study (clinicaltrials.gov Identifier: NCT03477110). For the comparison control of adjuvant TTF, adult patients age ≥ 18 years with newly diagnosed histologically-confirmed GBM that had a KPS ≥ 60 who received treatment with CRT and adjuvant TMZ + TTF from three institutions were included. The adjuvant TTF cohort excluded patients who progressed during CRT or did not receive TMZ. PFS and OS were compared between concurrent and adjuvant TTF patients. The impact of molecular mutations PTEN and TP53 were also evaluated. <h3>Results</h3> A total of 87 patients were enrolled in this study, of which 30 received concurrent TTF with CRT. Median patient age was 58 (range; 19-77) in the concurrent TTF group and 59 (range; 31-78) in the adjuvant TTF group. The median KPS in both groups was 90 (range 70-100 in concurrent, 60-100 in adjuvant). MGMT methylation was present in 33.3% (10) of the concurrent TTF and 32.0% (16) in the adjuvant TTF group. 40% (12) received GTR in the concurrent group and 38% (19) received GTR in the adjuvant group. Multifocal disease was appreciated in 40% (12) of patients in the concurrent TTF group, with one patient having gliomatosis. There is no significant difference in median OS, 17.1 months in the concurrent group and 19.4 months in the adjuvant group (p=0.38 [95% CI: 0.66-1.94]). There was also no significant difference in PFS, 10.2 months in the concurrent group and 9.7 months in the adjuvant group (p=0.76 [95%CI: 0.60-1.53]). Mutations in PTEN or TP53 did not impact OS or PFS of current vs adjuvant TTF treatment. <h3>Conclusion</h3> There is no OS or PFS difference between concurrent or adjuvant TTF treatment in patients diagnosed with glioblastoma in the current study. However, the adjuvant TTF group is considered to be a better prognostic group due to the elimination of patients that progressed or declined after initial CRT. The current study suggests concurrent TTF treatment may improve the outcome of a worse prognosis group to be similar to that of a better prognosis group. The survival benefit of concurrent TTF with CRT vs adjuvant TTF is being tested in the phase 3 TRIDENT EF 32 clinical trial (NCT04471844).

Molecular Markers Impacting Survival in Patients Receiving Concurrent Chemoradiation and Tumor-Treating Fields (TTF) in Patients with Newly Diagnosed Glioblastoma: Secondary Analysis of SPARE Trial

<h3>Purpose/Objective(s)</h3> SPARE trial (Scalp-sparing radiation with concurrent temozolomide and tumor treating fields; NCT03477110) is a single-arm pilot study that demonstrated the safety and feasibility of concurrent TTF with chemoradiation for newly diagnosed GBM. The current study is a secondary analysis evaluating the impact of molecular markers (PTEN, TP53, EGFR, and TERT) on overall survival (OS) and progression-free survival (PFS) of the patients in the trial. <h3>Materials/Methods</h3> This is a secondary analysis of SPARE trial. Molecular markers of histologically-confirmed, IDH-wildtype GBM patients age ≥ 18 years old with a KPS ≥ 60 who received concurrent chemoradiation and TTF followed by maintenance TMZ + TTF were evaluated. Molecular profile was evaluated with next-generation sequencing. Interaction of mutations in PTEN, TP53, EGFR, and TERT with TTF on OS and PFS was evaluated using a multivariable backward model. <h3>Results</h3> A total of 30 patients were enrolled in the SPARE trial, and 1 patient with IDH-mutant was excluded from the current analysis. All patients underwent concurrent TTF and chemoradiation. The median age is 58 (range; 19-77). The median KPS was 90 (range; 70-100). 9 patients (31.0%) have methylated MGMT promotor. 14 patients (48.3%) are found to have PTEN mutation, 9 patients (31.0%) with EGFR, 7 (24.1%) with TP53 mutation, and 23 patients (79.3%) with TERT mutated. MGMT methylation remained statistically significant for an increased OS (p=0.032; HR 7.18). TERT also had a statistically significant OS benefit (p=0.012; HR 7.60). MGMT and TERT also showed significant improvement in PFS. However, neither EGFR, TP53, nor PTEN showed any association of PFS or OS for patients who received concurrent TTF and chemoradiation treatment. <h3>Conclusion</h3> In this secondary analysis, patients with MGMT methylation showed better PFS and OS as expected. Neither EGRF, TP53, or PTEN mutation showed any association of PFS or OS. However, patients with TERT mutant showed improved OS with concurrent TTF with chemoradiation. A TERT mutation may be a new molecular biomarker in the described treatment approach. Due to the small sample size, further validation studies should be conducted.

Individualized combination therapies based on whole-exome sequencing displayed significant clinical benefits in a glioblastoma patient with secondary osteosarcoma: case report and genetic characterization

BackgroundThe incidence of osteosarcoma as a secondary neoplasm in glioblastoma patient is extremely rare. The genetic characteristic still remains unclear until now.Case descriptionWe reported a 47-year-old female patient with multiple intracranial disseminations and infiltrations (splenium of the corpus callosum and lateral ventricular wall) of a rapid progressive glioblastoma underwent occipital craniotomy and total resection of all the enhancing lesions. Whole-exome sequencing and pathological examination revealed glioblastoma, IDH1 wild type, PTEN deficient, TERT mutated, NF1mutated, MGMT unmethylated. After surgery, the patient received combined therapeutic regimen of TTFields (tumor-treating fields) plus pembrolizumab plus temozolomide and TTFields plus everolimus, which displayed significant clinical benefits. During the combined therapeutic course, an extremely rare secondary malignant neoplasm occurred, femur MR and pathological detection of biopsy tissue demonstrated osteosarcoma. The result of whole-exome sequencing revealed 7 germline mutated genes (EPAS1, SETD2, MSH3, BMPR1A, ERCC4, CDH1, AR). Bioinformatic analysis showed the two germline mutations (MSH3 and ERCC4) induced deficiency in the DNA repair machinery, which resulting in the accumulation of mutations and may generate neoantigens contributing to the development of a secondary osteosarcoma in this case.ConclusionIndividualized combination therapies based on whole-exome sequencing displayed significant clinical benefits in this case. Germline MSH3 and ERCC4 mutation may induce a secondary osteosarcoma in glioblastoma patients.

Glioma stem cell signature predicts the prognosis and the response to tumor treating fields treatment.

Glioma stem cells (GSCs) play an important role in glioma recurrence and chemo-radiotherapy (CRT) resistance. Currently, there is a lack of efficient treatment approaches targeting GSCs. This study aimed to explore the potential personalized treatment of patients with GSC-enriched gliomas. Single-cell RNA sequencing (scRNA-seq) was used to identify the GSC-related genes. Then, machine learning methods were applied for clustering and validation. The least absolute shrinkage and selection operator (LASSO) and COX regression were used to construct the risk scores. Survival analysis was performed. Additionally, the incidence of chemo-radiotherapy resistance, immunotherapy status, and tumor treating field (TTF) therapy response were evaluated in high- and low-risk scores groups. Two GSC clusters exhibited significantly different stemness indices, immune microenvironments, and genomic alterations. Based on GSC clusters, 11-gene GSC risk scores were constructed, which exhibited a high predictive value for prognosis. In terms of therapy, patients with high GSC risk scores had a higher risk of resistance to chemotherapy. TTF therapy can comprehensively inhibit the malignant biological characteristics of the high GSC-risk-score gliomas. Our study constructed a GSC signature consisting of 11 GSC-specific genes and identified its prognostic value in gliomas. TTF is a promising therapeutic approach for patients with GSC-enriched glioma.

P06.08.B Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy for glioblastoma

Abstract Background Glioblastoma is the most frequent primary brain tumor with dismal prognosis after standard treatment with surgery, and chemoradiation (the Stupp protocol). After a decade of failed clinical trials, tumor-treating fields have been first to show the added benefit of improved overall survival compared to the Stupp protocol (20.9 months vs 16.0 months). However, GBM remains a devastating disease, with almost inevitable recurrence, and limited options for second-line therapy. Radiation therapy (RT), is a standard therapy option for GBM, and it is used in most GBM cases affecting tumor through induction of DNA-damage. Recently, RT has been investigated as a mediator of T cell-based therapies in the context of immunosuppressive GBM microenvironment. The findings have shown promise in combination of T cell-based therapies, such as chimeric antigen receptor (CAR) T cell therapies, in improving the tumor infiltration, and penetration with immune cells. MET is a relevant oncogene in the context of GBM, being involved in stem-like properties, radiation response and resistance․ Hence, MET appeared to be a plausible target for combination with RT. In our research, we use MET-targeting CAR T cells (MET-CAR T cells) combined with radiation, and hypothesize synergistic interaction for GBM treatment. Material and Methods We used adherent (2D) and stem-like (3D) human GBM cell lines with different levels of MET expression. For MET-CAR T cell generation we did retrovirus-mediated transduction of activated human T cells and sorted the CAR-positive cells. We co-cultured MET-CAR T cells with GBM cells with or without RT, and assessed the killing and cytokine production in CAR T cells. Results Our results indicated that 5Gy radiation combined with MET-CAR T cells increases their potential in tumor cell killing. We observed increased CAR T cells effect at lower CAR T to target cells ratios when combined with radiation, even when radiation treatment did not lead to a significant decrease in viability. This phenomenon was similar across different types of cell lines (adherent, stem-like), different levels of MET expression, and different sensitivity to CAR T cells. We investigated the underlying mechanisms via intracellular cytokine measurement. We observed the most prominent response in TNF-α-expression. We also observed an increase in Granzyme B expression in co-culture with some of the GBM cell lines, especially in CD8+ subpopulation of CAR T cells. IFN-gamma expression increased in some adherent glioma cell lines but not in stem-like cell lines. Conclusion In conclusion, our data demonstrates the potency of MET-CAR T cells against GBM, and increased efficiency when combined with radiation. The suggested mechanism is the increased activation of T cells in TNF-α-dependent-manner. To validate these results we are testing our setup in an orthotopic mouse GBM model.

Feasibility of a method for optimizing the electrode array structure in tumor-treating fields therapy

Feasibility of a method for optimizing the electrode array structure in tumor-treating fields therapy

Modulation of Tumor-Treating Fields by Cerebral Edema from Brain Tumors

PurposeCerebral edema is an important component of brain metastasis, and its presence may alter the distribution of tumor-treating fields (TTFields). We therefore performed a computational study to model the extent of this alteration according to various edema conditions associated with the metastasis. Methods and MaterialsPostacquisition magnetic resonance imaging data sets were obtained from 2 patients with solitary brain metastases from non-small cell lung cancer. After delineation of various anatomies, a 3-dimensional finite element mesh model was generated and then solved for the distribution of applied electric fields, rate of energy deposition, and current density at the gross tumor volume (GTV), edema, and other cranial structures. Electric field–volume histograms, specific absorption rate–volume histograms, and current density–volume histograms were generated, by which plan quality metrics were derived from and used to evaluate relative differences in field coverage between models under various conditions. ResultsChanges in the conductivity of cerebral edema altered the electric fields, rate of energy deposition, and current density at the GTV region. At the cerebral edema region, increasing electric conductivity of the edema only decreased the electric fields and rate of energy deposition while the current density increased. The ratio of edema-to-tumor is also important because the plan quality metrics increased linearly when the edema-to-GTV ratio decreased, and increased vice versa. Furthermore, a conductive necrotic core additionally altered the distribution of TTFields according to the plan quality metrics. ConclusionsOur modeling study demonstrated that cerebral edema alters the distribution of applied TTFields in patients. Personalized treatment planning will need to take into account the modulating effects of cerebral edema on TTFields as well as additional effects from a necrotic core inside the GTV.

Tumor-treating fields in combination with sorafenib curtails the growth of colorectal carcinoma by inactivating AKT/STAT3 signaling.

BackgroundTumor-treating fields (TTFields) have been extensively used to treat various cancers as well as glioblastoma multiforme (GBM), owing to their antimitotic effects. Furthermore, sorafenib is also extensively used to treat hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC) and is under phase II/III clinical trials for other solid tumors. Hence, this investigation aimed to assess the efficacy of combination therapy with TTFields and sorafenib for colorectal carcinoma (CRC).MethodsHuman CRC HCT116 and SW480 cells were subjected to cell viability assay, followed by the assessment of their cell death using fluorescence-activated cell sorting (FACS) analysis. Furthermore, the expression of proteins involved in AKT/STAT3 signaling and apoptosis was assessed via western blotting.ResultsCombination treatment inhibited cell proliferation and induced apoptosis via Reactive oxygen species (ROS) generation, evident from caspase-3 cleavage in CRC cells and suppressed the AKT/STAT3 signaling pathway, as evident from downregulation of BCL-2 after post-treatment. The present results indicate that combination treatment with TTFields and sorafenib inactivates AKT/STAT3 signaling pathway, thus altering the expression of BCL-2, thus inducing apoptosis and inhibiting the growth of CRC cells.ConclusionsThus, combination treatment with TTFields and sorafenib is clinically applicable for treating metastatic CRC, although safety examination in patients with CRC will required to be achieved before this protocol can be implemented clinically for TTFields-sensitizer.

Tumor-Treating Fields in Glioblastomas: Past, Present, and Future.

Simple SummaryGlioblastoma (GBM) is the most common malignant primary brain tumor. Although the standard of care, including maximal resection, concurrent radiotherapy with temozolomide (TMZ), and adjuvant TMZ, has largely improved the prognosis of these patients, the 5-year survival rate is still < 10%. Tumor-treating fields (TTFields), a noninvasive anticancer therapeutic modality, has been rising as a fourth treatment option for GBMs, as confirmed by recent milestone large-scale phase 3 randomized trials and subsequent real-world data, elongating patient overall survival from 16 months to 21 months. However, the mechanisms of antitumor efficacy, its clinical safety, and potential benefits when combined with other treatment modalities are far from completely elucidated. As an increasing number of studies have recently been published on this topic, we conducted this updated, comprehensive review to establish an objective understanding of the mechanism of action, efficacy, safety, clinical concerns, and future perspectives of TTFields.Tumor-treating fields (TTFields), a noninvasive and innovative therapeutic approach, has emerged as the fourth most effective treatment option for the management of glioblastomas (GBMs), the most deadly primary brain cancer. According to on recent milestone randomized trials and subsequent observational data, TTFields therapy leads to substantially prolonged patient survival and acceptable adverse events. Clinical trials are ongoing to further evaluate the safety and efficacy of TTFields in treating GBMs and its biological and radiological correlations. TTFields is administered by delivering low-intensity, intermediate-frequency, alternating electric fields to human GBM function through different mechanisms of action, including by disturbing cell mitosis, delaying DNA repair, enhancing autophagy, inhibiting cell metabolism and angiogenesis, and limiting cancer cell migration. The abilities of TTFields to strengthen intratumoral antitumor immunity, increase the permeability of the cell membrane and the blood–brain barrier, and disrupt DNA-damage-repair processes make it a promising therapy when combined with conventional treatment modalities. However, the overall acceptance of TTFields in real-world clinical practice is still low. Given that increasing studies on this promising topic have been published recently, we conducted this updated review on the past, present, and future of TTFields in GBMs.

Small Molecules and Immunotherapy Agents for Enhancing Radiotherapy in Glioblastoma.

Glioblastoma (GBM) is an aggressive primary brain tumor that is associated with a poor prognosis and quality of life. The standard of care has changed minimally over the past two decades and currently consists of surgery followed by radiotherapy (RT), concomitant and adjuvant temozolomide, and tumor treating fields (TTF). Factors such as tumor hypoxia and the presence of glioma stem cells contribute to the radioresistant nature of GBM. In this review, we discuss the current treatment modalities, mechanisms of radioresistance, and studies that have evaluated promising radiosensitizers. Specifically, we highlight small molecules and immunotherapy agents that have been studied in conjunction with RT in clinical trials. Recent preclinical studies involving GBM radiosensitizers are also discussed.

Validation of Computational Simulation for Tumor-treating Fields with Homogeneous Phantom.

Tumor-treating Fields (TTFields) is a promising cancer therapy technique in clinical application. Computational simulation of TTFields has been used to predict the electric field (EF) distribution in the human body and to optimize the treatment parameters. However, there are only a few studies to validate the accuracy of the simulation model. Here we propose a measurement platform with technical details for validating the simulation model of TTFields. We further constructed homogeneous agar phantoms with different conductivity for voltage measurement. With the measured voltages from six equidistance recording points in the cylinder phantom, we calculated the EF intensity in the phantoms at different frequencies. Comparing the measured values with the simulated values obtained from two types of source simulation, we found that the current source simulation model of TTFields is a reliable method for evaluating the EF intensity distribution.

Synergetic Effect of Tumor Treating Fields and Zinc Oxide Nanoparticles on Cell Apoptosis and Genotoxicity of Three Different Human Cancer Cell Lines

Cancer remains a leading cause of death worldwide, despite extraordinary progress. So, new cancer treatment modalities are needed. Tumor-treating fields (TTFs) use low-intensity, intermediate-frequency alternating electric fields with reported cancer anti-mitotic properties. Moreover, nanomedicine is a promising therapy option for cancer. Numerous cancer types have been treated with nanoparticles, but zinc oxide nanoparticles (ZnO NPs) exhibit biocompatibility. Here, we investigate the activity of TTFs, a sub-lethal dose of ZnO NPs, and their combination on hepatocellular carcinoma (HepG2), the colorectal cancer cell line (HT-29), and breast cancer cell lines (MCF-7). The lethal effect of different ZnO NPs concentrations was assessed by sulforhodamine B sodium salt assay (SRB). The cell death percent was determined by flow cytometer, the genotoxicity was evaluated by comet assay, and the total antioxidant capacity was chemically measured. Our results show that TTFs alone cause cell death of 14, 8, and 17% of HepG2, HT-29, and MCF-7, respectively; 10 µg/mL ZnO NPs was the sub-lethal dose according to SRB results. The combination between TTFs and sub-lethal ZnO NPs increased the cell death to 29, 20, and 33% for HepG2, HT-29, and MCF-7, respectively, without reactive oxygen species increase. Increasing NPs potency using TTFs can be a novel technique in many biomedical applications.

The Routine Application of Tumor-Treating Fields in the Treatment of Glioblastoma WHO° IV

Introduction:Tumor-treating fields (TTFs) are a specific local oncological treatment modality in glioblastoma multiforme WHO° IV (GBM). Their mechanism of action is based on the effect of electrical fields interfering with the mitotic activity of malignant cells. Prospective studies have demonstrated efficacy, but TTF benefits are still controversially discussed. This treatment was implemented in our center as the standard of care in January 2016. We thus discuss the current state of the art and our long-term experience in the routine application of TTF.MethodsThe data of 48 patients suffering from GBM and treated with TTF were assessed and compared with previously published studies. Up-to-date information from open sources was evaluated.ResultsA total of 31 males and 17 females harboring a GBM were treated with TTF, between January 2016 and August 2021, in our center. In 98% of cases, TTFs were started within 6 weeks after concomitant radiochemotherapy (Stupp protocol). Mean overall survival was 22.6 months (95% CI: 17.3–27.9). Current indications, benefits, and restrictions were evaluated. Future TTF opportunities and ongoing studies were reviewed.ConclusionTTFs are a feasible and routinely applicable specific oncological treatment option for glioblastoma multiforme WHO° IV. Further research is ongoing to extend the indications and the efficacy of TTF.

Abstract 2037: Spatial omic changes of malignant pleural mesothelioma following treatment using tumor-treating fields

Abstract Background: Application of alternating-electric fields as cancer-directed therapy known as Tumor-Treating Fields (TTFields) has been shown to be effective by exerting dipole alignment forces on polar microtubule subunits and dielectrophoretic forces in the cytokinetic furrow. This effect results in disruption of mitosis at the cellular level, and at the clinical level with significantly prolonged overall survival of patients with glioblastoma and malignant pleural mesothelioma (MPM). The molecular alterations that occur at the genomic and transcriptomic levels following TTFields treatment are unknown. We applied a spatial omics approach to elucidate spatial intratumoral effects of TTFields at the molecular level in regions of interest (ROI) in a mouse model of MPM. Methods: Eight Balb/C mice were injected with AB1 MPM cells until sizable tumors were observed (2-3 weeks). TTFields were applied, with heat sham used as a negative control. After 14 days (6 days of treatment, 2 days of rest, then 6 more days of treatment) tumors were resected, fixed and paraffin embedded. Following the Nanostring GeoMx protocol, thin sections of all eight tumors were placed on a slide, and incubated with both Ki-67 antibodies, and a GeoMx Mouse Cancer Transcriptome Atlas RNA probe set. Using Ki-67 staining as a guide, 12 ROIs were selected across each tumor to capture intratumoral heterogeneity, including the core and periphery of each tumor The DSP barcoded RNA probes were cleaved, sequenced and analyzed. We compared differential expression of subset gene classes of TTFields vs heat sham treated tumors; results were further stratified into Ki-67 high and low subsets for each sample. Results were assessed by Gene Set Enrichment. Results: Sham-treated tumors grew to over 300 mm3; TTFields-treated tumors averaged 100 mm3, confirming anti-tumor effect. Gene Set Enrichment Analysis uncovered upregulation of genes associated with interferon-alpha and -gamma responses in TTFields-treated tumors, which also displayed downregulation of pathway components associated with glycolysis, mTOR signaling, oxidative phosphorylation, cell invasion, hypoxia, and TNF-alpha signaling. Spatial analysis detected a heterogeneous response and differential expression between different portions of tumors. Conclusions: TTFields application induces clear patterns of differential expression in the transcriptome of treated tumors, including an increasingly immune-stimulated tumor microenvironment that also affects molecular pathways critical to cellular proliferation and invasion. These findings point the way toward improved understanding of timing and sequences of TTFields in relation to systemic cytotoxic, targeted, and immune modulation forms of therapeutic strategies. Our finding of upregulated immune response implicates TTFields as a potential synergistic tactic when coupled with immunotherapeutic approaches. Citation Format: Emil Lou, Katherine Ladner, Kerem Wainer-Katsir, Karina Deniz, Yaara Porat, Boris Brant, Shiri Davidi, Yuki Padmanabhan, Phillip Wong, Amrinder Nain, Clifford J. Steer, Moshe Giladi. Spatial omic changes of malignant pleural mesothelioma following treatment using tumor-treating fields [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2037.

Abstract 4138: Prediction of progression-free survival in patients with primary glioblastoma: MRI T2 relaxivity and deep learning

Abstract Introduction: We aimed to evaluate T2 relaxation times in the follow-up of patients with glioblastoma (GBM), the most common and aggressive primary brain tumor with nearly universal recurrence following standard therapy. Methods: In this partially retrospective study, 53 patients (mean age 45.05 years ± 12.6) with non-recurrent GBM followed at our department roughly every 2 months after surgery and combined chemo-radiotherapy were included (&amp;gt;180 days progression-free survival [PFS] as determined by RANO,1 ≥3 MRI examinations in the PFS interval [same scanner and protocol]). Thirty-six patients additionally received Tumor-Treating Fields (TTFields) therapy. All data used were prior to progression. T2 relaxation rates (1/T2) were calculated voxel-wise assuming mono-exponential decay. Whole-brain (WB) histogram values were extracted from 1/T2 maps including skewness, kurtosis, mean, median, 15 and 85 percentile values and variance. We additionally segmented 1/T2 maps using a 5 compartment Gaussian mixture model (Python v3.8.2), producing mean, variance and voxel percentage for each component. To evaluate predictive potential with respect to PFS, we used a deep recurrent neural network (long short-term memory [LSTM] model) in Tensorflow v2.3.1 (4 timesteps); the features used included the above metrics as well as TTFields treatment status and scanner. Twenty subjects were included in the predictive model, as inclusion criteria were stricter (progression, ≤120 days between all MRIs [mean 43.6 days], ≥4 PFS MRIs). Two models were tested: a regression model (days to progression) and a classification model (±18 months PFS; models differed in output layer). Both models were run 10 times; mean results are presented. Results: We found WB median 1/T2 correlated with PFS, as values decreased prior to progression. WB median 1/T2 linear regression slopes also differed in progression versus pseudo-progression, as values were relatively stable in pseudo-progression. The deep LSTM regression model achieved an R2 of 97%. The deep LSTM classification model achieved a mean macro precision of 86%, recall 85% and F1 accuracy of 85% in predicting progression within 18 months. Conclusions: We found very intriguing results with WB median 1/T2 measurements in distinguishing progression from pseudo-progression, and in suggesting progression despite otherwise unremarkable imaging. A more complex predictive model trained on pre-progression data, using a fully-automated segmentation method followed by deep learning, showed very promising results. The present results may find utility in the monitoring of GBM patients and may be advantageous to include in multimodal predictive models. Reference: 1. Wen PY et al. J Clin Oncol 2010;28:1963-1972. Citation Format: Aaron M. Rulseh, Josef Vymazal. Prediction of progression-free survival in patients with primary glioblastoma: MRI T2 relaxivity and deep learning [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4138.

Technical note: Evaluation of methods for reducing edge current density under electrode arrays for tumor-treating fields therapy.

Tumor-treating fields (TTFields) therapy is increasingly utilized clinically because of its demonstrated efficacy in cancer treatment. However, the risk of skin burns must still be reduced to improve patient safety and posttreatment quality of life. The purpose of this study was to evaluate the methods of constructing electrode arrays that reduce current density exceeding threshold values, which can cause skin burns during TTFields therapy. Electrode and body models were generated using COMSOL software. The body model had the dielectric properties of the scalp. The average current density beneath the central region of the electrode was maintained at ∼31mA/cm2 RMS. The deviations in current density at the edges of the electrode were reduced by three methods: adjustment of the ceramic thickness ratio of the center to the edge from 1/5 to 4/5, adjustment of the radius of the metal plate from 5.0 to 8.0mm, and insertion of an insulator of width 0.5 to 2mm at the edge. While using a single circular electrode, adjustment of the ceramic thickness ratio, adjustment of the metal plate radius, and insertion of an insulator near the edge reduced the deviations of current density by 14.6%, 67.7%, and 75.3%, respectively. Similarly, while using circular electrode arrays, inserting an insulator at the edge of each electrode reduced the deviations of current density significantly, from 8.62 to 2.40mA/cm2 . Insertion of an insulator at the edge of each electrode was found to be the most effective method of attaining uniform current density distribution beneath the electrode, thereby lowering the risk of adverse effects of TTFields therapy.