Of the many devastating side effects of metastatic cancer, bone pain seems the most common. Almost all patients with metastatic prostate cancer have skeletal metastases and 90% of patients with progressive breast cancer develop these painful and debilitating lesions.

Current pain treatments consist of systemic therapy (analgesics, chemotherapy, hormonal therapy and bisphosphonates) and local treatments (radiation, surgery and more recently, radio frequency ablation).

One company is taking on the challenge of alleviating the pain, and the positive results are becoming evident in studies. InSightec (Tirat Carmel, Israel) reported that new publications show that magnetic resonance-guided focused ultrasound (MRgFUS) with the ExAblate system has the potential to be an effective noninvasive pain-relieving treatment for tumors that have spread to the bones (bone metastases).

The results of a 31-patient study appear in the Nov. 11 online issue of Annals of Surgical Oncology, while data from an 11-patient subgroup analysis of that study were published separately in the October issue of Radiology.

"We believe these early results provide substantial rational for our ongoing pivotal study," Nadir Alikacem, InSightec's VP of global regulatory affairs/chief regulatory officer, told Medical Device Daily.

"These patients are in the final stages of cancer and we believe it's vital to maintain the quality of their lives without the side effects associated with radiation and analgesics," he said. "Bone metastases are the leading cause of cancer pain and we believe that ExAblate may provide these patients a non-invasive, radiation free treatment."

Alikacem added: "Our goal is not to cure their cancer, but to help them live out the rest of their lives without suffering from their bone pain."

During the ExAblate treatment, the physician uses MRI with registered CT images to visualize the patient's anatomy and then aims focused ultrasound waves at the tumor to relieve the pain. The MRI allows the physician to monitor and continuously adjust the treatment in real time. The patient is consciously sedated to alleviate pain and minimize motion.

The focused ultrasound waves are focused down onto a small area of the painful bone. This causes the bone surface to heat up and destroys the tissue. The focused ultrasound is then targeted to another area next to the treated location and this new area is treated.

The process is repeated several times until the nerves in the bone surface of the painful bone tumor are destroyed. Due to the high acoustic absorption and low thermal conductivity of the bone cortex, it is possible to use a low level of energy and still achieve a localized heating effect that will relieve the pain while minimizing damage to adjacent tissue, InSightec said.

"The increasing longevity of the population, along with the rise in cancer incidence during the last decade and ever-improving treatment outcomes for primary cancers, contributes to the growing number of patients living with metastatic bone disease," said Boaz Liberman, MD, head of orthopedic oncology of Sheba Medical Center (Tel Hashomer, Israel) and lead author of the 31-patient analysis.

"Increasing focus on cancer patients' quality of life has led to a search for effective pain-relieving treatments with fewer short- and long-term side effects," he said. "These preliminary results suggest that the ExAblate treatment using MRgFUS has the potential to provide a safe and effective noninvasive treatment for patients suffering from painful bone metastases."

InSightec is currently enrolling patients into an FDA-approved Phase III pivotal study to confirm these earlier results. It expects to enroll 148 subjects with bone metastases who are not candidates to radiation treatments into the study at centers throughout the U.S. and around the world.

Alikacem shared with MDD InSightec's plans for the future of the ExAblate after the Phase III study is conducted. "If the data are positive, as expected, we plan to file a pre-market application with the FDA. We also remain focused on the uterine fibroids indication, for which the system is currently approved and used commercially. "

He said the company also has begun an FDA Phase IV study pertaining to fibroids. "The purpose of this multi-site randomized clinical study is to determine if ExAblate treatment can help women with non-hysteroscopically resectable uterine fibroids who are diagnosed with unexplained infertility become pregnant. Women in this study will be randomized with myomectomy surgery," he said.

The ExAblate is currently used commercially as a treatment for symptomatic uterine fibroids. The system received the CE mark for uterine fibroids in 2002 and FDA approved the system as a treatment for symptomatic uterine fibroids in 2004.

More than 4,500 symptomatic women have been treated with the ExAblate to date, with 92% reporting symptom relief up to 36-months after treatment. The ExAblate system received CE-mark certification for pain palliation of bone metastases in June 2007.