Trial Testing Ultrasound for Brain Cancer Liquid Biopsies

(National Science Foundation)

15 Dec. 2022. A clinical trial is underway testing the safety and feasibility of focused ultrasound to enable use of blood tests to monitor a patient’s glioblastoma, a form of brain cancer. The study is conducted in North America by Insightec in Haifa, Israel, developer of ultrasound technology for diagnosis and treatment of neurological diseases and other disorders.

Glioblastoma is an aggressive cancer with tumors forming in astrocyte cells in the brain. This type of cancer is considered difficult to treat, with surgery, radiation, chemotherapy, or other targeted drugs designed mainly to slow progression of the disease. National Brain Tumor Society says glioblastoma accounts for about half (49%) of malignant primary brain tumors, with some 13,000 cases expected this year in the U.S.

Diagnosis and monitoring of glioblastoma today requires tissue biopsies, taking samples of tumor cells during surgery for analysis. While liquid biopsies — use of blood tests to detect and monitor cancer — are advancing for other solid tumors, blood draws for glioblastoma are hampered by the blood-brain barrier that prevents cancerous cells from the tumor from entering the blood stream. The blood-brain barrier acts as a security system for the brain, where walls of blood vessels in the brain have physical and chemical properties that regulate interactions with other functions in the body. In this case, the blood-brain barrier prevents glioblastoma tumors cells with characteristic DNA from entering the blood stream, limiting use of liquid biopsies.

Low-intensity focused ultrasound

Insightec adapts ultrasound, focused sound waves, aimed at disease targets for treatments and diagnostics. For diseases in the brain, company’s technology called Exablate Neuro, uses MRI images and algorithms to guide focused ultrasound to deliver up to 1,024 waves to precise locations. In the U.S. the Food and Drug Administration has cleared Exablate Neuro for treating some forms of Parkinson’s disease and essential tremors. In many cases, says Insightec, the treatments can be given in an outpatient facility.

The new clinical trial is testing an Exablate system to send low-intensity focused ultrasound or FUS waves into glioblastoma tumors, with the goal of disrupting the blood-brain barrier enough to allow tumor cells to enter the patient’s blood stream. The trial is enrolling 57 patients diagnosed with glioblastoma at six sites so far in the U.S. and Canada. The study team is taking blood samples before and after the ultrasound treatments, looking primarily for changes in circulating free DNA in the blood samples. The team is also tracking any adverse effects of the treatments and correlating the liquid biopsies with tissue biopsy results. The study has no control or comparison group.

Insightec says the trial’s first patients are now enrolled at the Mayo Clinic in Rochester, Minnesota and Sunnybrook Health Sciences Centre in Toronto. “If successful, this work has the potential to substantially decrease the risk of obtaining the initial diagnosis, says Terry Burns, a neurosurgeon at Mayo Clinic, in an Insightec statement released through Cision. “Importantly, FUS can be repeated non-invasively, allowing a rare molecular window into individual patient’s brain tumors as they evolve during treatment.”

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