Long-term Spinal Cord Stimulation Outcomes Using Fast-acting Sub-perception Therapy Designed to Engage Surround Inhibition

Introduction: Novel Fast-Acting Sub-Perception Therapy (FAST) has demonstrated robust and rapid (seconds to minutes) onset of analgesia in chronic pain patients implanted with Spinal Cord Stimulation (SCS) systems (1-3). On the basis of preclinical data, FAST-SCS is thought to specifically engage the Surround Inhibition mechanism of action to mediate the suppression of chronic pain (4). Correspondingly, precise stimulation location and optimal neural dose is required to generate analgesia using Fast-Acting Sub-Perception Therapy (FAST). We studied the effectiveness of FAST and additional SCS therapy options for chronic pain in a prospective, multicenter, single-arm clinical study and in this report describe long-term outcomes.

Methods: The FAST study is a prospective, multi-center, single-arm study (with adaptive design) of patients implanted with SCS systems (WaveWriter Systems, Boston Scientific) for chronic pain. The primary endpoint is based on the targeted pain responder rate (≥50% reduction) 3-months post-activation with no increase in average daily opioid medications. Secondary endpoints include (but are not limited to) patient satisfaction (Patient Global Impression of Change, PGIC) and other functional outcomes including disability (Oswestry Disability Index, ODI) and sleep. Key inclusion criteria include diagnosis of predominant neuropathic pain of trunk and/or limbs for at least 6-months, and no back surgery within 6-months prior to screening.

Results: The primary endpoint (p < 0.0001) was met as demonstrated by 80% (16/20) of a prespecified cohort of patients achieving a ≥50% reduction in targeted pain with no increase in opioid medications at 3-months follow-up. To date, a total of 56 patients have been assessed at baseline. In those patients who so far have reached 24-months follow-up (n=20), a mean 4.9-point reduction in VRS low back pain score was observed corresponding to a mean score of 7.4 at baseline which decreased to 2.6 (p < 0.0001). In addition, a 31-point mean improvement in ODI score at 24-months follow-up was determined. Consistently high levels of patient satisfaction were also found at all follow-up timepoints (>85% reporting much or very much improved). Updated long-term outcomes data that has since been collected and analyzed is now planned for presentation.

Conclusion: With availability of multiple modalities in SCS systems, the capability for rapid onset of analgesia is particularly useful in evaluating what may be best suited for patients. Preliminary results from this ongoing FAST prospective study suggest that profound, significant pain relief along with improvement in functional outcomes may be achieved in chronic pain patients with FAST-SCS therapy and additional SCS therapy options.