By Lina carolina 
A significant breakthrough in the fight against glioblastoma, one of the most aggressive and difficult-to-treat brain cancers, has emerged from research led by Keck Medicine of USC. A novel combination therapy, integrating Tumor Treating Fields (TTFields) with immunotherapy and chemotherapy, has demonstrated a remarkable potential to extend survival for patients diagnosed with this devastating condition. Glioblastoma carries a grim prognosis, with the National Brain Tumor Society reporting an average survival rate of a mere eight months following diagnosis. This new research offers a beacon of hope for a patient population with limited effective treatment options.
The core of this innovative approach lies in the synergistic action of three distinct therapeutic modalities. Tumor Treating Fields (TTFields) are delivered via a wearable device that generates targeted low-intensity electric fields directly into the tumor. These fields are designed to disrupt the cellular machinery that drives tumor growth and proliferation. Simultaneously, the therapy aims to signal the body’s immune system, drawing its attention and resources to the cancerous cells. When this TTFields therapy is combined with the immune-boosting power of immunotherapy, specifically pembrolizumab, and the established cytotoxic effects of chemotherapy, such as temozolomide, a significantly enhanced anti-tumor response is observed.
The Science Behind Tumor Treating Fields
Tumor Treating Fields operate on a unique principle that sets them apart from conventional cancer treatments. The therapy utilizes low-intensity, alternating electric fields that are precisely tuned to interfere with the division of tumor cells. These electric fields create forces within the cells that repeatedly push and pull key internal structures, such as chromosomes and other vital components, in constantly shifting directions. This dynamic disruption makes it exceedingly difficult for the cancer cells to replicate and multiply, effectively halting their uncontrolled growth. By preventing tumor progression, TTFields create a more favorable environment for the body to mount a defense and for other therapies to become more effective.
In the context of glioblastoma treatment, TTFields are delivered through a set of specially designed mesh electrodes. These electrodes are strategically positioned on the patient’s scalp, creating a focused electrical field that targets the brain tumor with a specific frequency and intensity. Patients are typically required to wear the TTFields device for approximately 18 hours a day, a regimen that underscores the commitment required for this therapy. The continuous application of these fields is believed to be crucial for maintaining the disruptive effect on tumor cells.
Harnessing the Immune System: A Critical Shift
A key observation from the Keck Medicine study is how TTFields appear to enhance the infiltration of tumor-fighting T cells into and around the glioblastoma. T cells, a crucial component of the adaptive immune system, are responsible for identifying and neutralizing cancerous cells. The researchers found that TTFields actively attract these vital immune cells to the tumor site. When this enhanced T cell presence is followed by the administration of immunotherapy, such as pembrolizumab, the T cells not only remain active for longer periods but are also replenished by even more potent and effective tumor-fighting T cells. This creates a sustained and amplified immune assault on the cancer.
Dr. David Tran, MD, PhD, Chief of Neuro-Oncology at Keck Medicine, Co-Director of the USC Brain Tumor Center, and the corresponding author of the study, elucidated the significance of this interaction. "By using TTFields with immunotherapy, we prime the body to mount an attack on the cancer, which enables the immunotherapy to have a meaningful effect in ways that it could not before," Dr. Tran explained. He further emphasized, "Our findings suggest that TTFields may be the key to unlocking the value of immunotherapy in treating glioblastoma." This statement highlights a fundamental challenge in glioblastoma treatment: the inherent resistance of the tumor to existing immunotherapies when used in isolation.
Historically, TTFields have often been used in conjunction with chemotherapy in various cancer treatments. However, even with these aggressive approaches, the overall prognosis for glioblastoma has remained exceptionally poor. Similarly, immunotherapy, while a revolutionary treatment for many other forms of cancer, has shown limited efficacy when applied to glioblastoma as a standalone therapy. The current study proposes a paradigm shift by demonstrating that the combination of these three modalities can overcome these limitations.
Unprecedented Survival Data and Implications for Unresectable Tumors
The most compelling outcome of this research is the observed increase in overall survival. In this study, the addition of immunotherapy to the established TTFields and chemotherapy regimen was associated with a remarkable 70% increase in overall survival. This statistic represents a significant leap forward in a field characterized by incremental gains.
Perhaps even more encouraging are the findings related to patients with larger, unresected glioblastomas. These patients, who often have the poorest prognoses due to the inability to surgically remove their tumors, showed an even stronger immune response to the TTFields and consequently lived longer. This suggests that a larger tumor burden might, paradoxically, provide more targets for the TTFields to initiate and amplify the immune response. This is a critical development, as surgery is not always an option for glioblastoma patients, particularly when tumors are located in functionally critical areas of the brain or have spread extensively.
The Mechanics of Overcoming the Blood-Brain Barrier
To fully appreciate the impact of this research, it is essential to understand the unique biological challenges posed by glioblastoma. Pembrolizumab, the immunotherapy agent employed in this study, functions as an immune checkpoint inhibitor (ICI). ICIs work by releasing the brakes on the immune system, enabling T cells to more effectively identify and attack cancer cells. However, glioblastomas create a formidable barrier to this immune attack.
Originating within the brain, these tumors are often shielded from the body’s natural immune surveillance by the blood-brain barrier (BBB). This highly selective physiological barrier meticulously regulates the passage of substances from the bloodstream into the brain, protecting it from pathogens and toxins. Unfortunately, the BBB can also impede the entry of vital immune cells, such as T cells, and therapeutic agents that could otherwise combat brain tumors. This creates an immunosuppressive microenvironment within and around the glioblastoma, rendering standard treatments like pembrolizumab and chemotherapy significantly less effective.
Dr. Tran’s hypothesis for circumventing this challenge was to initiate an immune reaction directly within the tumor itself, a strategy known as "in situ immunization." The TTFields therapy, by attracting and activating T cells within the tumor’s confines, appears to achieve precisely this. The study’s findings strongly support this concept, demonstrating that the combination of TTFields and immunotherapy effectively triggers a potent immune response within the tumor. This localized immune activation then provides a robust foundation for ICIs to amplify, thereby bolstering the body’s intrinsic defense mechanisms against cancer.
Dr. Tran vividly illustrated this dynamic with a sports analogy: "Think of it like a team sport — immunotherapy sends players in to attack the tumor (the offense), while TTFields weaken the tumor’s ability to fight back (the defense). And just like in team sports, the best defense is a good offense." This analogy effectively captures the collaborative and mutually reinforcing action of the combined therapies.
Study Methodology and Rigorous Data Analysis
The findings presented are derived from an analysis of data from the 2-THE-TOP Phase 2 clinical trial. This trial enrolled 31 patients who had been newly diagnosed with glioblastoma and had completed chemoradiation therapy, a standard initial treatment for many brain tumors. Of these participants, a significant cohort of 26 patients received the experimental combination therapy: TTFields alongside both chemotherapy and immunotherapy. Notably, seven of these 26 patients had tumors that were deemed inoperable due to their anatomical location, representing an especially high-risk subgroup with historically poor prognoses and very limited treatment alternatives.
The treatment protocol involved a sustained application of therapies. Patients received six to 12 monthly cycles of chemotherapy, administered concurrently with TTFields, for a duration of up to 24 months. The number and duration of these treatments were individualized, determined by each patient’s response to the therapy. The immunotherapy, pembrolizumab, was administered every three weeks, commencing with the second dose of chemotherapy, and continued for up to 24 months.
The results of this trial were statistically significant. Patients who received the TTFields device in conjunction with chemotherapy and immunotherapy experienced an approximate 10-month increase in survival compared to historical control groups who had used the device with chemotherapy alone. This improvement is substantial, considering the aggressive nature of glioblastoma. Furthermore, patients with large, inoperable tumors exhibited an even more pronounced benefit, living approximately 13 months longer. These patients also demonstrated significantly stronger immune activation in response to the therapy, a finding that directly correlates with the observed survival advantage.
"Further studies are needed to determine the optimal role of surgery in this setting, but these findings may offer hope, particularly for glioblastoma patients who do not have surgery as an option," Dr. Tran stated, acknowledging the need for continued research while emphasizing the immediate potential impact for a vulnerable patient group.
Moving Towards Larger Scale Validation: The Phase 3 Trial
The promising results from the Phase 2 trial have paved the way for larger, more definitive research. Keck Medicine is actively participating in a multicenter Phase 3 clinical trial designed to rigorously validate the efficacy of the TTFields, immunotherapy, and chemotherapy combination. Dr. Tran, a long-standing advocate and researcher of TTFields for over a decade, is at the helm of this crucial initiative, serving as the chair of the steering committee for this Phase 3 trial. Dr. Frances Chow, MD, a neuro-oncologist with USC Norris, is leading the efforts at the Keck Medicine study site as the principal investigator.
This Phase 3 trial is a substantial undertaking, currently enrolling patients across 28 sites in the United States, Europe, and Israel. The trial aims to recruit over 740 patients by April 2029. A key aspect of this larger trial is its inclusion of patients with varying degrees of tumor resection – including those with gross total resection, partial resection, or biopsy-only tumors. This design will allow researchers to assess the extent to which surgical removal of tumors influences the immune response to the combined therapy, providing a more comprehensive understanding of its applicability across different surgical scenarios.
The collaborative nature of this research is further highlighted by the contributions of several authors from the Keck School of Medicine of USC, including Dongjiang Chen, PhD, an assistant professor of research neurological surgery; Son Le, PhD, an assistant professor of research neurological surgery; Harshit Manektalia, a research programmer; Ming Li, PhD, a professor of research population and public health sciences; and Adam O’Dell, a research lab specialist. Additionally, colleagues Ashley Ghiaseddin, MD, and Maryam Rahman, MD, MS, from the University of Florida, contributed significantly to this work.
The research was made possible through funding from Novocure, the manufacturer of the Optune device, the TTFields system utilized in this study. Dr. Tran has also received honoraria from Novocure for his consultant work. Furthermore, Dr. Chen and Dr. Tran are listed as inventors on two patent applications related to the work reported in this study, underscoring their foundational role in developing this therapeutic approach. The convergence of academic research, industry partnership, and robust clinical trials is crucial for translating scientific discoveries into tangible benefits for patients facing life-threatening diseases like glioblastoma. The ongoing Phase 3 trial represents a critical step in solidifying this promising combination therapy as a new standard of care.
