NICE, France — In a 2-year follow-up of a study using a new device for deep brain stimulation (DBS) to treat Parkinson's disease (PD), improvement in motor function was sustained, and the reduction in anti-parkinsonian medication was stable.
"At 6 months, the benefit runs closer to 49%, out 2 years you're looking at around 46, 47%," Jerrold Vitek, MD, PhD, University of Minnesota, Minneapolis, reported here at the International Congress of Parkinson's Disease and Movement Disorders.
"The meds dropped about 33%," he added. "In the United States, we tend not to drop meds for some reason as much as the Europeans do, which generally you're going to find probably 50%, maybe 60% in European studies."
The mean Unified Parkinson's Disease Rating Scale-III (UPDRS-III) score was 43.4 at pre-trial screening and 22.6 at 2 years in the stimulation on/medication off condition (46% improvement; P < .001)
The device in the study (Vercise DBS System, Boston Scientific) contains multiple, independent current sources that allow for selective activation of individual contacts on the DBS lead to provide a defined distribution of current. The trial used the device to deliver bilateral subthalamic nucleus stimulation.
Earlier 52-week, open-label results of the 12-week INTREPID study, a prospective, double-blind, multicenter, randomized trial, were presented last year and reported by Medscape Medical News at the time.
These 2-year results follow up those from the blinded phase of the study. Those initial results showed an improvement in the treatment group vs controls (between baseline and 12 weeks) in the number of waking hours per day with good symptom control and no troublesome dyskinesia as recorded on a PD diary, with no increase in anti-parkinsonian medications.
In the initial phase, 160 patients were randomly assigned 3:1 to active intervention or to sham stimulation of 1 second, just so that the device would register a stimulus to blind the controls to their group assignment. After 12 weeks, all participants received active, open-label treatment.
Patients included in the study had bilateral idiopathic PD, 5 years or greater of motor symptoms, a Hoehn & Yahr score of 2 or greater, and a UPDRS-III score of 30 or higher off medication. They had 6 or more hours per day of poor motor function, a 33% or greater improvement on UPDRS-III following medication, and were good surgical candidates for bilateral subthalamic nucleus DBS.
At baseline, the mean age of the patients was 59.9 ± 7.95 years, with 43.1% younger than age 60, 72.5% male, and a disease duration of about 10 years.
On the Global Impression of Change scale, "physicians saw about 95% of patients felt they were satisfied [or] extremely satisfied with their outcome," Vitek said. "Then you ask the patients, and again, it's sitting pretty close to about 90%, and that's maintained for the 2 years."
He noted that despite the fact that physicians considered only about 3% of patients worsening over the 2 years, 6% of patients thought their symptoms had worsened at 6 months, increasing to 9.3% and then 10.6% of patients at year 1 and year 2, respectively.
Levodopa equivalents were stable during the 2-year follow-up, going from 1477 mg at baseline, to 1041 mg at 6 months, 1021 mg at 1 year, and 1011 mg at 2 years (P < .001).
Infections within the first 6 months after surgery associated with partial or total hardware removal occurred in 3.6% of patients, and intracranial hemorrhage in 2%. Infections were generally at the site of the leads; with other device studies, infections more often occurred at the site of the implantable pulse generator (IPG).
Vitek speculated that since the IPG is rechargeable, it contains a smaller battery and could be made smaller and round, with less chance for infection at the IPG implantation site.
Five deaths occurred in the study and were unrelated to the study device or implant procedure.
Vitek said that with other devices and electrodes, current will flow in the direction of the least impedance, such as an area of tissue with higher impedance.
"With this system, you can control each contact separately and distribute the way you want it to be distributed," Vitek explained. And he said that over the time of the study, other device manufacturers had been adding more contacts, "so people are finding advantages to adding contacts."
Susan Fox, MB ChB, PhD of University Health Network, Toronto, Canada, commented to Medscape Medical News, "Technology is advancing, and the methods of trying to personalize the way DBS is delivered to the individual patients is something that is being improved, and I think that to me is the take-home message."
Michael Schwarzschild, MD, PhD, of Massachusetts General Hospital, Boston, commended the study design.
"The fact, as I think Dr Vitek highlighted, [is] that this is one of the few double-blind studies," of DBS, he said. "I think it spoke to the idea that in DBS, a little bit like exercise, it's an area that has traditionally not had the level of rigor in clinical trial design. So from what I could see, [the study] was aspiring to it and probably achieved some of that."
The study was funded by Boston Scientific. Vitek has consulted for and/or received honoraria from Boston Scientific, Medtronic, and Abbott Laboratories. Fox and Schwarzschild have disclosed no relevant financial relationships.
International Congress of Parkinson's Disease and Movement Disorders (MDS) 2019: Abstract 228. Presented September 23, 2019.
https://www.medscape.com/viewarticle/919011#vp_1
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