High intensity focused ultrasound (HIFU) is a non-invasive therapeutic technique that can destroy a tumor without surgery or causing damage to other tissues.
Now, a scientist at the University of Texas Southwestern Medical Center is not only expanding the use of HIFU in Texas, but also exploring new ways to use it to deliver chemotherapy directly to a specific target in brain tumors and pediatric cancers.
Rajiv Chopra was recruited in 2012 to UT Southwestern Medical Center from Sunnybrook Research Institute and the University of Toronto with a Rising Star Award from CPRIT.
With HIFU, sound waves pass into the body through the skin and are focused to destroy a tumor with heat. Unlike radiation, the technique doesn’t damage intervening normal tissue, and heats only where the sound waves are focused.
HIFU is often used in combination with Magnetic Resonance Imaging (MRI), which can sensitively detect temperature changes with in the human body.
“With this combination, you have a device that doesn’t use radiation and doesn’t have to penetrate the body, but it can heat and destroy a tumor,” says Chopra. “Not only that, the physician can see and direct the HIFU treatment in real time.”
Once the tumor is destroyed, the body’s immune system takes over, breaks down the dead tissue, and disposes of it. A patient may experience swelling and inflammation but there is usually no risk of infection. Patients can go home the same day, and their recovery time is measured in days rather than weeks.
Chopra explained that HIFU is a great technique to use in combination with early detection of localized tumors, such as a lump in the breast or prostate. Surgical treatment of these tumors might require a radical mastectomy or removal of the prostate, while HIFU accomplishes the same goals of eliminating the tumor but without surgery.
Since it uses no radiation, this combination is also great for treating pediatric cancers, he says.
Chopra is using his CPRIT award to advance the use of HIFU to direct chemotherapy to the brain and increase the effectiveness of chemotherapy for other tumors. He says that HIFU can temporarily increase the permeability of the blood-brain barrier, allowing chemotherapy drugs to cross into the brain when they would otherwise be kept out.
Chemotherapy drugs can also be encapsulated within nanoparticles that completely enclose the drug at body temperature. But when these are slightly heated using HIFU, they become leaky and let the drug out precisely where a physician directs it.
This targeted chemotherapy technique is particularly valuable in pediatric cancers, where physicians want to minimize their patient’s overall exposure to toxic chemicals.
Knowing this, Chopra sought out a pediatric oncologist with whom to collaborate. He and Dr. Theodore Laetsch have conducted studies in animals and are now starting a clinical trial of HIFU-targeted chemotherapy in pediatric patients who suffer from relapsed solid tumors.
“This is a perfect example of translational medicine,” says Chopra. “We leveraged the CPRIT investment to get federal and foundation support and now we’re beginning a clinical trial.” Dr. Chopra’s research efforts led to the world’s first human trials of transurethral MR-HIFU, a novel minimally-invasive method for the treatment of localized prostate cancer. The technology is currently being developed by Profound Medical Corporation, and pivotal trials for FDA approval in the U.S. were recently completed in early 2018.
Chopra finds the scientific environment at UT Southwestern Medical Center to be unusually collaborative between the basic sciences and medicine. “It’s a culture that’s very unique,” he says.
Chopra received his undergraduate degree in physics from McMaster University in Ontario, and Ph.D. in medical biophysics from the University of Toronto. He was a postdoc at the University of Toronto and joined the faculty in the same department in 2006, the same year he joined the Sunnybrook Institute in imaging sciences.
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