A non-invasive technique designed to send chemotherapy medication through the protective barrier surrounding the brain has been successfully trialed for the first time on a patient with brain cancer. Using an “ultrasonic screwdriver,” this technique is a huge improvement on an earlier method trialed last year, as announced by the Toronto-based researchers.
The blood-brain barrier is a lattice-like network that acts to keep harmful things like pathogens out of the brain, while allowing useful substances through. It's very good at doing its job, but unfortunately that represents a hurdle in medicine: If a person has a cancerous tumor inside the brain, getting drugs through without compromising it proves impossible. Last year, however, researchers made an incredible breakthrough, somewhat literally: The blood-brain barrier was breached for the first time using a technique that left it intact post-procedure.
Medical scientists from the Pitié-Salpêtrière Hospital in Paris placed special emitters that would generate a certain frequency of sound – ultrasound, beyond our hearing capabilities – inside the brains of four people with a malignant brain tumor (a glioblastoma). Miniscule bubbles, or “microbubbles,” were then injected into the patients, and allowed to bump up against the normally impenetrable blood-brain barrier.
The high-intensity focused ultrasound emitters were then activated, causing the microbubbles to expand and contract about 200,000 times per second. This forced apart the cells that make up the barrier’s lattice, allowing a chemotherapy drug to make it through the barrier and treat the tumor. The ultrasound emitters were placed as close to the tumor as possible, and the barrier is only weakened for two minutes or so over a small patch, leaving the rest of the brain protected.
Although effective, the treatment wasn’t particularly precise, and it did require an “invasive” technique: implanting ultrasound emitters into the brain. This new revised method, developed by Dr. Todd Mainprize and Dr. Kullervo Hynynen at Sunnybrook Hospital in Toronto, is more precise and non-invasive.
Firstly, as before, chemotherapy medication is injected into the bloodstream, as are the microbubbles. After locating the target tumor using an MRI scanner, a focused beam of ultrasound from outside of the body is directed at the blood-brain barrier, allowing the microbubbles to vibrate and open an incredibly small section of it up, allowing the medication to get through. The bubbles are eventually reabsorbed into the lungs. Importantly, no surgery of any kind was involved.
Last week, the procedure was trialed on the first of ten subjects with brain tumors, a middle-aged woman. 24 hours after the breach was initiated, the tumor and the surrounding tissues were sampled and removed surgically, then sent to a laboratory to examine how much of the medication reached the target areas.
If this trial proves to be effective, safe, and feasible, this non-invasive technique will revolutionize neurosurgery, and not just for cancer treatments: Alzheimer’s disease is another target for this ultrasound-based method, and already, in-roads are being made.
