A leap forward in radiation therapy for brain tumors

According to the National Cancer Institute’s 2020 Annual Report to the Nation, advances in cancer therapies continue to improve survival rates for patients with overall cancer death rates from 2013-2017 and decline for men, women, children and adolescents, and young adults.

As people with cancer live longer, it is more important than ever for healthcare providers to understand and manage the short- and long-term side effects of treatments and their impact on quality of life. They must consider the unique safety profile of new cancer therapies and treatment combinations.

President Biden’s federal budget proposal for 2022 called for $6.5 billion to create a new health agency focused on cancer and other diseases. The proposal states, “This major investment in federal research and development would drive transformational innovation in health research and accelerate the adoption and implementation of health breakthroughs.” These kinds of developments will undoubtedly change the way cancer is treated in the future as researchers develop more targeted therapies, immunotherapies, advanced surgical techniques and newer forms of radiation therapy.

Radiation therapy for brain tumors

According to cancer.net, an estimated 24,530 adults in the United States will be diagnosed with a primary cancer of the central nervous system. This is in addition to the more than 700,000 people currently living in the US with a cancerous or non-cancerous brain tumor. Brain metastases, or cancers that start elsewhere in the body and spread to the brain, are much more common than primary brain tumors, with an estimated 150,000 to 200,000 people developing brain metastases each year, and the incidence is increasing due to more effective cancer diagnostics and treatments .

External radiation therapy (EBRT) is most commonly used to treat brain tumors. The radiation is usually delivered by a linear accelerator, a machine that radiates from the outside inwards, thus crossing harmless bystander tissue as it enters and, in most cases, leaves the body. There are inevitably side effects associated with this, including, but not limited to, fatigue, hair loss, skin changes, nausea, vomiting, brain swelling, and even permanent neurocognitive changes. For radiation oncologists and their patients, the potential toxicities of EBRT are accepted in exchange for the opportunity for improved tumor control.

While improvements in systemic therapies such as chemotherapy and immunotherapy, especially when combined with radiation therapy, help people live longer with brain cancer, the brain often serves as a refuge where resistant tumor cells continue to migrate, making recurrence common. Trying to give a second or third course of radiation therapy for recurrent brain tumors carries a significant risk of complications; sometimes it is impossible to offer further irradiation of the brain even with the most advanced EBRT technologies, such as stereotactic radiosurgery.

There are opportunities to increase the therapeutic ratio beyond traditional EBRT methods.

Internally administered radiation therapy, or brachytherapy, in which radioactive seeds are placed directly into the brain, has many theoretical advantages. With internally administered radiation therapy, there is no irradiation of harmless brain tissue of bystanders by the in or out of rays. When administered intraoperatively, brachytherapy provides targeted and immediate treatment, rather than the several weeks of surgical wound healing required before starting EBRT, during which residual tumor cells are allowed to grow.

Despite these advantages, traditional intracranial brachytherapy has limited acceptance. It requires expertise and extensive experience from the physician; few are willing or qualified to perform the therapy. In its traditional form, brachytherapy seeds deliver an intense radiation dose to adjacent brain tissue, often leading to necrosis or death of normal tissue. This is very problematic and requires prolonged steroid use, reoperations or can even cause death.

Intracranial brachytherapy has recently been improved by the development of a surgically targeted radiation therapy consisting of Cesium-131 ​​radiation seeds embedded in a bioresorbable collagen tile. Similar to traditional brachytherapy, these seed-bearing tiles are placed intraoperatively, allowing the radiation sources to begin treating any remaining tumor cells immediately after tumor removal.

Unlike traditional brachytherapy, the collagen carrier material surrounding the seeds serves as a structural compensation to prevent the radiation seeds from not only migrating, but also delivering supratherapeutic radiation doses at the seed-brain interface, minimizing potential complications. The selection of a radioisotope with shorter half-life, Cesium-131, versus the traditionally used iodine-125, allows for a rapid delivery of radiation dose that may be more suitable for the treatment of rapidly growing malignancies such as glioblastomas and brain metastases.

Clinical studies have demonstrated improved local tumor control and progression-free survival, and the potential for improved overall survival with this latest treatment approved by the FDA for use in patients with resectable, newly diagnosed malignant brain tumors and recurrent brain tumors.

Initiatives to refine existing technologies with innovative technical solutions and collaboration between specialties, such as the advances of surgically targeted radiation therapy described above, are needed now more than ever in the fight against cancer. As the incidence and recurrence rates of brain tumors and other cancers continue to rise, there is an increasing need to improve radiation options by making treatments safer and more effective.

With a federal call to action to make great strides in developing new treatments for society’s most common diseases and conditions, the health care community should boldly improve existing therapies to help patients not only live longer, but also lead a better and healthier life .

Editor’s Note: The author is director of medical science at GT Medical Technologies, which developed the therapy described in the article.

Photo: Eraxion, Getty Images

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