Treatment with magnetic resonance image-guided focused ultrasound (MRIgFU) ablation therapy significantly reduced pain in 67% of patients who received the treatment. The device, ExAblate, uses numerous small ultrasound beams that are designed to converge on a tumor with bone, heat it, and destroy it. Results of a clinical trial of this therapy were presented at the 2013 annual meeting of the American Society of Clinical Oncology in early June in Chicago, Illinois.

Patients with cancer that has spread to their bones often are treated with radiation therapy to reduce pain. However, if that treatment does not work or cannot be used again, this therapy now offers a second and effective option.

“Pain is a common, often debilitating symptom of the spread of cancer to bones. We are pleased to now have a second therapy that can improve a patient’s enjoyment of life,” said principal investigator Mark Hurwitz, MD, of Thomas Jefferson University in Philadelphia, Pennsylvania. A number of cancers spread to bones, and a substantial proportion of patients live for years with these metastases, which can have a profound impact on a patient’s quality of life, he added.

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The findings of the trial led to approval of ExAblate last October by the US Food and Drug Administration as second-line therapy for palliation of painful metastatic bone tumors. The first-line therapy is typically radiotherapy.

“The response to ExAblate was as good as radiotherapy, which was notable because it is very unusual to see a second-line treatment with a response rate that is as high as first-line therapy,” Hurwitz said.

He added that use of ExAblate offers several advantages compared to other ablative therapies. “It is noninvasive and provides more detailed anatomic information so that we can visualize the complete beam path to make sure that critical structures such as vessels and nerves are not in the way,” said Hurwitz. “We are also able to monitor the temperature in the tumor as well as in nearby normal tissues so that we do not inadvertently heat normal organs and tissues.”

ExAblate has also been approved for treatment of uterine fibroids.

The study led by Hurwitz was a multicenter, randomized and placebo-controlled phase III clinical trial. The 142 patients who enrolled either could not undergo, or had not responded to, radiation treatment.

Three months after ExAblate therapy, 67% of treated patients reported significant improvement in pain, compared to 21% in the placebo arm. They typically rated their pain as “much improved” or “very much improved,” Hurwitz said. A quality of life assessment also measured significant improvement.

“The treatment is given just once, and a response occurs within days,” he said. “There are a lot of patients who could potentially benefit from MR guided focused ultrasound.”