Spinal Cord Stimulators for Chronic Pain May Not Live Up to the Hype

Among patients with chronic pain, use of a permanent spinal cord stimulator (SCS) was not associated with a reduction in opioid use or nonpharmacologic pain interventions compared with conventional medical management (CMM), a retrospective comparative effectiveness study showed.

After propensity matching, those who had a permanent SCS implanted had higher odds of chronic opioid use during the first 12 months compared with those treated with conventional strategies (adjusted OR 1.14, 95% CI 1.01-1.29), according to researchers led by Sanket S. Dhruva, MD, MHS, of the University of California San Francisco School of Medicine.

SCS patients also had lower odds of epidural and facet corticosteroid injections (aOR 0.44, 95% CI 0.39-0.51), radiofrequency ablation (aOR 0.57, 95% CI 0.44-0.72), and spine surgery (aOR 0.72, 95% CI 0.61-0.85) during the first 12 months, the group wrote in JAMA Neurology.

But there were no significant differences at months 13 to 24 between the two groups:

• Chronic opioid use: aOR 1.06 (95% CI 0.94-1.20)
• Epidural and facet corticosteroid injections: aOR 1.00 (95% CI 0.87-1.14)
• Radiofrequency ablation: aOR 0.84 (95% CI 0.66-1.09)
• Spine surgery: aOR 0.91 (95% CI 0.75-1.09)

“The lack of reduction in pharmacotherapy, epidural and facet corticosteroid injections, and radiofrequency ablations at 2 years among patients receiving SCS compared with those receiving CMM suggests that SCS was providing insufficient pain relief to forego other therapies or improve rates of depression or anxiety, as prescriptions for these drug classes did not decline,” Dhruva and team wrote.

Furthermore, “total costs of care in the first year were $39,000 higher with SCS than CMM and similar between SCS and CMM in the second year,” they noted.

“The findings appear to belie the popular belief that SCS may result in reduced opioid medication usage or overall fewer physician visits in the years immediately following device implant,” pointed out Prasad Shirvalkar, MD, PhD, and Lawrence Poree, MD, PhD, MPH, both of the University of California San Francisco, in an accompanying editorial.

Despite increasing use of SCS, evidence of its superiority over usual care is limited, Dhruva and colleagues wrote. Most SCS devices have been authorized by the FDA without clinical data, with approximately 85% of large studies (>100 patients) being industry funded, they added, characterizing the current research as “a rare study that is relatively free from such conflicts of interest.”

According to the editorialists, “it is important to note that absence of evidence does not necessarily equal evidence of absence for a potential overall health outcomes difference between the two therapies.”

“Variables, such as opioid usage or follow-up visits, pose a potential confound of circular logic, as these variables are also likely strong surrogates for healthcare utilization and, therefore, cost. If patients are being matched across cohorts based on variables that may track cost themselves, it should not be surprising that costs across groups do not differ substantially,” they continued.

Shirvalkar and Poree also pointed out a potential sampling bias in the initial SCS cohort — given the increasing numbers of patients that disenrolled from the SCS starting cohort from the 2018 index year (when 55% were disenrolled) overlapped with recent adoption of potentially more effective high-frequency SCS — “similar outcomes and cost after 2 years may preferentially reflect outcomes using older, less effective SCS therapy.”

“Prior data on healthcare utilization and cost suggest that the current authors may have detected a significant non-QALY [quality-adjusted life-years]-adjusted difference between SCS and CMM if their analyses were extended by 12 more months (to 3 years) or included direct measures of quality of life, such as the EQ-5D,” they wrote.

For this real-world study, Dhruva and colleagues used administrative claims data on 7,560 patients diagnosed with failed back surgery syndrome, complex regional pain syndrome, chronic pain syndrome, and other chronic postsurgical back and extremity pain from April 2016 through August 2018.

The researchers matched insured participants 1:5 to SCS (n=1,260) or CMM (n=6,300). Mean age was 63.5 years, and 59.3% were women.

During the 2-year study, SCS-related complications occurred in 18% of patients, and 22% required device revisions and/or removals, 10% of which were not for complications, “suggesting lack of effectiveness,” the authors noted.

Study limitations acknowledged by both the authors and editorialists included the absence of direct measures of pain or function, or quality-adjusted life-years, to assess comparative therapeutic benefits.