A groundbreaking, proof-of-concept technique that allows biomarkers from a brain tumor to pass through the tough blood-brain barrier into a patient’s blood using noninvasive focused ultrasound and some tiny bubbles, potentially eliminating the need for a surgical biopsy has been developed by the researchers at Washington University School of Medicine in St. Louis. The blood test would reveal the amount of mRNA in the blood, which gives physicians specific information about the tumor that can help with diagnosis and treatment options. The researchers tested their theory in a mouse model using two different types of the deadly glioblastoma brain tumor. They targeted the tumor using focused ultrasound, a technique that uses ultrasonic energy to target tissue deep in the body without incisions or radiation.

Similar to a magnifying glass that can focus sunlight to a tiny point, focused ultrasound concentrates ultrasound energy to a tiny point deep into the brain. Once they had the target - in this case, the brain tumor - researchers then injected microbubbles that travel through the blood (lat. Sanguis) similar to red blood cells. When the microbubbles reached the target, they popped, causing tiny ruptures of the blood-brain barrier that allows the biomarkers from the brain tumor to pass through the barrier and release into the bloodstream. A blood sample can determine the biomarkers in the tumor.

This technique could lead to personalized medicine. Having the ability to monitor the changing molecular events of the tumor in an ongoing way allows the researchers to not only better diagnose a tumor in the brain but to follow its response to different types of treatment. Physicians can also collect the blood and detect the expression level of biomarkers in the patient. It enables them to perform molecular characterizations of the brain tumor from a blood draw and guide the choice of treatment for individual patients.

This noninvasive focused ultrasound-enabled liquid biopsy technique can be useful for long-term monitoring of brain cancer (lat. Carcinoma) treatment response, where repeated surgical tissue biopsies may not be feasible. Meanwhile, variations within tumors pose a significant challenge to cancer biomarker research.

Focused ultrasound can precisely target different locations of the tumor, thereby causing biomarkers to be released in a spatially-localized manner and allow the researchers to better understand the spatial variations of the tumor and develop better treatment. The team continues to work to refine the process. The future will require integration with advanced genomic sequencing and bioinformatics to enable even more refined diagnostics. The ongoing work is to optimize the technique and evaluate its sensitivity and safety.