Improved Focus – Radiology Today Magazine

Improved FocusBy Beth W. OrensteinRadiology TodayVol. 18 No. 8 P. 24MR-guided focused ultrasound is proving to be a safe, effective treatment for tumors in children and young adults.Teams of physicians are using two modalities that are very well known to radiologists—MRI and ultrasound—to design pediatric tumor interventions that are more precise and less invasive than current methods. Among others, researchers at the Sheikh Zayed Institute for Pediatric Surgical Innovation at Children’s National Health System in Washington, D.C., and Nicklaus Children’s Hospital in Miami are studying the use of MR-guided focused ultrasound (MRgFUS) for the treatment of relapsed solid tumors, benign bone tumors, and benign brain tumors in children and young adults.Focused ultrasound is not new. According to the Focused Ultrasound Foundation, one of the first approved applications was to treat uterine fibroids in women; the application was approved by the FDA in 2004. In 2012, the FDA approved the technology for the relief of pain associated with cancer that has spread to the bone. And, in 2015, the FDA approved two focused ultrasound systems for the ablation of prostate tissue.”You can imagine that high-intensity focused ultrasound [HIFU] would have even greater benefit in the pediatric space because it is delivered without ionizing radiation and surgery,” says Peter Kim, MD, CM, PhD, vice president of the Sheikh Zayed Institute at Children’s National, who leads its Image-Guided Non-Invasive Therapeutic Energy program. “As physicians, our mission is always to make pediatric care more precise, less invasive, and pain-free.”Researchers at Children’s National are looking at MRgFUS, which typically uses a HIFU beam, to treat pediatric osteoid osteomas, benign tumors that usually develop in the long bones of the leg—femurs or tibias—but can occur in any bone. Between 7% and 20% of cases occur in the spine. In most cases, osteoid osteomas are small—less than 2 cm. The tumors are painful, says Karun Sharma, MD, PhD, director of IR at Children’s National.”It’s very classic bone pain,” he says. “No trauma is associated with it. The pain happens at night, so it wakes them up.” Nonsteroidal anti-inflammatory drugs (NSAIDs) can provide some relief, but it is temporary, Sharma says. “This pain can last for years and years, and we don’t want to give kids or adolescents strong doses of NSAIDs for that long because of all the side effects.”In the ’70s and ’80s, surgeons would scrape the tumor from the bone or remove the affected part of the bone. The surgery would often result in collateral damage “and patients often had to be on crutches and bed rest for a long time,” Sharma says. In the ’90s, radiofrequency ablation (RFA) became a better option. While RFA is less invasive than surgery, it still requires drilling through muscle and soft tissue into bone. “It is a very good treatment and 90% to 95% effective,” he says.Pushing the Envelope Two years ago, the researchers at Children’s National wanted to “push the envelope” and so they began trials to see whether MRgFUS would be an even better option to locally treat both benign osteoid osteomas and malignant solid tumors. The researchers have treated 12 patients. “We are very pleased with the success of the treatments so far,” Sharma says. “We have been able to show that it is a very safe treatment.” The next step for the osteoid osteoma study, Sharma says, is to compare MRgFUS head to head with RFA. “We suspect the results will be similar, but there are thousands of cases of RFA recorded and only 30 of MR-HIFU. We have to look at MR-HIFU more closely and in more detail.”The clinical trial in solid tumors, led by AeRang Kim, MD, PhD, a pediatric oncologist at Children’s National, also includes desmoid tumors. Desmoid tumors are benign but very locally aggressive soft tissue tumors. Their recurrence rate after surgery is high, and medical therapies have not demonstrated substantial effectiveness, AeRang Kim says.The patients in the MRgFUS studies don’t have tumors that are close to the spine or the brain. “We wouldn’t want to risk any thermal or heat injury to the spinal cord,” Sharma says. Tumors in the pelvis also would be hard to reach, he adds. One patient with a tumor in the inside of the pelvis had to be excluded from the osteoid osteoma trial because he couldn’t be positioned in the machine to make delivering the ultrasound feasible, Sharma says.The patients receive a CT or MRI scan prior to the procedure so that the physicians can identify the target area that needs to be heated and destroyed. Interventional radiologists who perform ablations understand how to use HIFU to heat the tissue, Sharma says. “But this is a different type of ablation, and you do have to learn how to plan the treatment and avoid any critical structures. It is something that the interventional radiologist can pick up, but there is a learning curve.” MR provides real-time guidance to the tumor target, and therma

Source: Improved Focus – Radiology Today Magazine

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