Postmarketing studies of VNS yielding no surprises so far.
Updates on the two studies of the implantable vagus nerve stimulation (VNS) system in patients with treatment-resistant depression were provided by the manufacturer, Cyberonics, and the Food and Drug Administration, during a portion of a meeting of the FDA's Neurological Devices Panel in January.
In July 2005, the VNS device, previously approved for treating seizures, was approved for adjunctive long-term treatment of chronic or recurrent depression in patients aged 18 and older who are experiencing a major depressive episode and have not had an adequate response to four or more antidepressant treatments.
The approval came with several conditions, including the requirement that Cyberonics conduct a 1-year randomized dose-ranging study and a 5-year observational registry study.
The FDA's decision to approve the device for depression has been questioned by health advocacy groups. A U.S. Senate Finance Committee investigation concluded last year that the device had been approved for the depression indication over the objections of FDA staff scientists and medical officers.
As of Dec. 31, 2006, 89 patients had been enrolled in the 1-year study, a multicenter, double-blind trial comparing the safety and effectiveness of adjunctive VNS administered at three electrical charges for 54 weeks in patients with treatment-resistant depression (TRD). The study is supposed to enroll 460 patients at 30 sites, but because of problems with reimbursement for the device and implantation surgery, the company is planning a voluntary program to donate the device and surgery so that the study can be completed in time, said Dr. Richard Rudolph, vice president, clinical and medical affairs, and chief medical officer at Cyberonics.
On Feb. 5, shortly after the panel meeting, the Centers for Medicare and Medicaid Services announced that there was sufficient evidence to show that vagus nerve stimulation was neither reasonable nor necessary for treating resistant depression. The agency said it planned to issue a national noncoverage determination for the use of VNS for this indication and requested public comments on the issue. VNS is covered by Medicare and Medicaid when used for epilepsy.
The 18-month report submitted to the FDA by Cyberonics included serious adverse events reported through Jan. 9: One report showed worsening depression after implantation, compared with five before implantation. There were no reports of suicide ideation after implantation, compared with one such report before implantation. There has been one case each reported in patients after implantation of suicide attempt, wound infection, chest pain, death (a motor vehicle accident), and thyroid carcinoma, compared with no such cases reported preimplantation, Dr. Rudolph said. The FDA presented the same data.
To date, enrollment in the registry is on schedule, he said. As of Dec. 31, 264 patients--223 with implants--had been enrolled in the long-term prospective, observational, multicenter, patient outcome registry, which is following the clinical course and outcomes for patients with TRD, with and without adjunctive VNS therapy. The plan is to enroll 1,000 patients who receive VNS and follow them for 60 months, along with 1,000 patients with treatment-resistant depression who do not receive VNS.
To date, he said, the early safety and effectiveness data from the postmarketing studies "are consistent with the results" of the preapproval studies."
During the open public hearing session of the meeting, Diana Zuckerman, Ph.D., president of the National Research Center for Women and Families, said that since the approval of the VNS device for depression was based on weak research, the postmarketing studies were critical. She added that she hoped that the FDA would pay as much attention to the data from these studies as they did to premarketing studies.
Also speaking during the session, Dr. Peter Lurie of Public Citizen's Health Research Group said the need for a study comparing different electrical charges indicated that the data submitted for approval were "inadequate" and that because the registry is uncontrolled and unblinded, the efficacy of VNS will remain unresolved.
In June 2004, the neurological devices panel supported approval of the device, with conditions. Those supporting approval agreed that the data were not ideal, but said there was reasonable assurance that the device was safe and that studies provided enough evidence of effectiveness that VNS should be made available to treatment-resistant patients.
But the panel members advocated the registry study collect more data on the device.
BY ELIZABETH MECHCATIE
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|Title Annotation:||News; vagus nerve stimulation|
|Publication:||Clinical Psychiatry News|
|Date:||Mar 1, 2007|
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