Patients with painful diabetic peripheral neuropathy of the lower extremities can experience significant reductions in pain symptoms over the longer term with spinal-cord stimulation (SCS), new results from a 5-year prospective study indicate.
The trial of almost 50 patients implanted with a spinal-cord stimulator showed that 55% of patients met the criteria for “treatment success” in terms of reducing pain at 5 years and that 80% were still using their device at this time point.
Senior author Maarten van Kleef, MD, PhD, department of anesthesiology and pain medicine, Maastricht University Medical Center, the Netherlands, told Medscape Medical News: “I saw all the patients myself for the trial, and I was impressed by the burden of those patients. They have terrible pain, especially at night, and when spinal-cord stimulation is successful that is reduced to almost zero.”
But the work also showed that those with the highest Michigan Diabetic Neuropathy Score (MDNS) at baseline were almost four times as likely to experience treatment failure and have the device removed than those with lower scores.
Dr van Kleef said those with the most severe pain respond less well due to the types of nerve fibers involved as the diabetic peripheral neuropathy progresses.
Consequently, he believes that determining a patient’s MDNS score prior to considering the implant can help guide doctors in the selection of patients for this invasive and expensive treatment option.
The research was published online November 6 in Diabetes Care, by Maarten van Beek, also of Maastricht University Medical Center, and colleagues.
A Sustainable Treatment Modality for the Majority of Patients
SCS was initially suggested as a last-resort treatment for painful diabetic peripheral neuropathy in 1996, and, although its efficacy has been shown in two randomized controlled trials, there are no prospective data on its long-term impact.
Moreover, there is evidence to suggest that up to 60% of patients may experience ongoing pain or require further interventions over the longer term and that SCS is ineffective in progressive painful diabetic peripheral neuropathy.
The researchers therefore conducted a multicenter, prospective study of patients with painful diabetic peripheral neuropathy who had MDNS score assessed alongside other baseline characteristics and then initially underwent test implantation with the SCS octapolar lead (Octad, Medtronic) under local anesthesia.
Those who experienced a ≥50% reduction in pain scores on a numerical rating scale (NRS) or had a Patient’s Global Impression of Change (PGIC) score of ≥6 after a 2-week trial period were then fitted with either the Synergy Versitrel or PrimeAdvanced spinal-cord stimulators (Medtronic).
Outcomes were assessed after 12 months and every year until 5 years, with treatment success defined as pain relief of ≥50% during the day and night for 4 days on the NRS and a PGIC score of ≥6 for pain and sleep.
From an initial 137 painful diabetic peripheral neuropathy patients screened, 48 met the inclusion criteria and underwent trial stimulation. Of those, 40 reported initial success and received a permanent SCS implant.
The mean age was 57.4 years, and 37.5% were female. The majority (89.6%) of patients had type 2 diabetes, and the average duration of the disease at baseline was 13.3 years; they had been experiencing pain as a result of their diabetic neuropathy for 5.4 years, with a mean NRS score at baseline of 6.5.
After 1 year, there was a significant reduction in pain scores, with a mean NRS pain score during the day of 3.8 and a mean night score of 3.9 (P < .0001). At 5 years, the mean day score was 4.3 and the mean night score was 4.6.
Of the patients, 86% experienced treatment success at 1 year, falling to 71% at 2 years, 77% at 3 years, 67% at 4 years, and 55% at 5 years; 80% of patients with a permanent implant were still using their device after 5 years.
Cost-effective Treatment if Battery Lasts 4 Years
Those with a higher baseline MDNS score were almost four times more likely to suffer treatment failure and subsequent SCS device removal (hazard ratio, 3.9; P = .014), although the authors note that not everyone with extremely severe pain failed — 40% of those with the highest MDNS score still used the SCS device after 5 years.
And conversely, those with higher baseline NRS scores at night were less likely to fail treatment (hazard ratio, 0.8; P = .045).
Two patients experienced SCS device infection, eight underwent one battery replacement, and five had two battery replacements over the study periods.
Furthermore, 10 patients reported pain in the subcutaneous battery pocket, with one patient experiencing considerable discomfort.
Dr van Kleef explained that the SCS devices typically cost around €25,000 (~$30,000) in the Netherlands and that the ultimate cost-effectiveness depends on how much the patient uses it.
“The battery has an average lifetime of 4 to 5 years, but some patients stimulate much higher; they only have a battery lifetime of 1 or 2 years, and in those patients it is not cost-effective.
“But when you divide the cost of the implant over 4 years, it is cost-effective.”
He noted that, owing to the high cost of the device, use is limited in some countries, with, for example, only around 1500 to 2000 implanted in the Netherlands.
This compares with thousands implanted every year at just one institution in the United States, the Cleveland Clinic.
“We try to reserve it for very severe pain, and diabetic polyneuropathy is a very severe pain,” he explained.
He reiterated that, when the patients are well selected, “It is a very good” option “for a subpopulation of diabetic polyneuropathy.”
Dr van Kleef believes that spinal-cord stimulation could become more widely available if the cost of the device were to fall. However, he pointed out that he has been implanting the devices since 1985, “and I see that the prices are the same.”
This study was supported by Medtronic. The authors report no relevant financial relationships.
Diabetes Care. Published November 6, 2017. Abstract
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