Nancy A. Melville

March 23, 2015

NATIONAL HARBOR, MD — Patients with severe chronic pain who undergo implantation with an investigational high-frequency spinal cord stimulation (SCS) device show twice the magnitude of pain relief and remission compared with those receiving a conventional, lower-frequency SCS device, according to results from the first randomized clinical study of the technology.

"Spinal cord stimulation has been used for approximately 40 years, and this is the first randomized, pivotal study in its history," said coauthor B. Todd Sitzman, MD, MPH, from Advanced Pain Therapy, Hattiesburg, Mississippi.

"The [high-frequency SCS device] demonstrated statistical superiority to traditional SCS by a wide margin for all primary and secondary endpoints."

The results were presented here at the American Academy of Pain Medicine (AAPM) 31st Annual Meeting. The study was supported by Nevro Corp.

High-Frequency System

The multicenter US SENZA clinical trial compared an implantable high-frequency SCS system that delivers 10,000 Hz of stimulation (Senza HF10, Nevro) with a system that is currently approved in the United States, delivering a stimulation of 50 to 100 Hz (Precision Plus, Boston Scientific).

The HF10 system is available in Australia and Europe and is under investigation for approval by the US Food and Drug Administration.

For the study, 198 patients at 10 centers in the United States with severe, chronic pain of the trunk and/or limbs who had not responded to therapy for 3 or more months were randomly assigned to implantation with the high-frequency (n = 101) or standard (n = 97) SCS.

Patients had average back and leg pain intensity of 5 or higher out of 10 on the visual analogue scale (VAS).

Ninety patients in the high-frequency SCS group and 81 in the standard SCS group were included in the final analysis.

Measures of back pain, assessed according to VAS scores, were significantly reduced in both groups at 3, 6, 9, and 12 months, but scores of back pain with high-frequency SCS were consistently lower at all time points (2.5 vs 4.3 at month 12, respectively).

Improvements in back pain relief according to changes in VAS scores from baseline showed similar patterns in favor of the high-frequency SCS, with 66.4% in that group reporting relief at month 12 compared with 44.7% in the traditional SCS group (P < .001 at all endpoints).

"Historically, back pain has been a very difficult treatment outcome to achieve. Even at best it is difficult to achieve paresthesia overlap of back pain with conventional SCS, but there was a marked increase in VAS scores in the traditional as well as [the HF10] arm," Dr Sitzman said.

"The 66% improvement with HF10 is significant because these are patients who have failed medical management and conventional therapies."

Similar improvements in leg pain were seen for VAS-reported pain and change in score for pain relief with the high-frequency SCS at all assessments (P < .001).

Responder rates, defined as the percentage of people who achieved 50% or greater improvement, for patients in the HF10 group were significantly higher at all endpoints (78.7% vs 51.3% for back pain and 78.7% vs 51.3% for leg pain at 12 months; all P < .001).

"These findings bode well for SCS therapy as a whole, showing it is effective in patients with back and leg pain, but HF10 was superior in back and leg pain at 3, 6, and 12 months," Dr Sitzman said.

Dr Sitzman noted that the high-frequency SCS system has some important differences from the traditional system in addition to the significantly higher frequency. For example, the leads are placed according to anatomic landmarks in the spinal column, meaning that mapping in the operating room according to paresthesia-induced sensations is not needed.

"Whereas traditional SCS is based on the reliability of paresthesia overlap with the areas of pain, patients in this study said they didn't even feel when this when it was on compared to off," he said.

Dr Sitzman said the safety profile with the high-frequency system is similar to that of conventional SCS.

In a separate poster presented at the meeting, researchers reported that tissue damage can occur when the stimulation pulse charge exceeds the safe range, but such ranges are not used with the investigational system.

"Charge/phase and charge density of HF10 therapy (typically 0.08 μC/phase and 0.6 μC/cm2, respectively) are well within the established safe range and much lower than traditional low-frequency SCS," the authors write.

They noted that the extensive use of the high-frequency device in Europe and Australia has also shown no safety concerns.

"More than 2,500 patients have received HF10 therapy, some for less than four years, with no safety issues regarding 10 kHz stimulation, including no related device failures such as lead or battery failures," the authors note.

Battery Recharge a Compliance Issue?

One concern about the higher-frequency system is how frequently the battery needs to be charged, Hemant Kalia, MD, MPH, from the Interventional Pain & Cancer Rehabilitation Specialist at the Unity Spine Center, Rochester, New York, told Medscape Medical News.

"One of the biggest challenges we have seen with this is the recharge rate," he said.

"Since the frequency is so high, patients have to recharge their batteries almost on a daily basis, which comes as a barrier of adaptation."

The recharging can become a serious compliance issue, he noted.

"Especially in the elderly population, for instance, compliance can become a problem if they don't want to charge it, and eventually may just stop using it."

"There is no doubt that, as far as the clinical efficacy, the high-frequency approach is superior," he added. "The technology is much more efficacious, but I think more research has to be done in improving the quality of the battery."

In addressing the question from the audience at his presentation, Dr Sitzman said patients with the HF10 typically need to recharge every 3 or 4 days. "But it is patient-dependent, based on the individual response," he said.

Aside from the battery issue, however, Dr Kalia said the study is particularly important in being the first of its kind.

"In the field of neuromodulation, this is the first ever randomized controlled trial, so it has been highly anticipated," he said.

The study received support from Nevro Corp. Dr Sitzman and Dr Kalia have disclosed no relevant financial relationships.

American Academy of Pain Medicine (AAPM) 31st Annual Meeting. Abstract 140. Presented March 20, 2015.

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