DETACHABLE BALLOON CLINICAL TRIAL ONE-YEAR FOLLOWUP REQUIREMENT ENDORSED BY SEVERAL FDA PANEL MEMBERS; GROUP DISAGREES ON NEED FOR DATA STRATIFICATION
This article was originally published in The Gray Sheet
Executive SummaryDetachable balloon clinical trials should have at least one- year followup, members of FDA's neurological devices panel suggested at a June 11 meeting in Rockville, Maryland. When asked by FDA to make a recommendation on the amount of followup that should be required for detachable balloon therapy patients, Harold Wilkinson, MD, PhD, University of Massachusetts Medical School, Worcester, said that he would like "a minimum of a year, but I'd also like to see five-year followup" done on the patients. Although the panel did not make a specific recommendation regarding followup, several members agreed with Wilkinson's assessment that one year of followup should be required in premarket studies, augmented by five-year followup in postmarket surveillance studies. The followup issues were discussed while the panel addressed questions posed by the agency regarding a June 4 draft guidance for the evaluation of the detachable balloons, which are used to occlude brain arteries in order to treat aneurysms and fistulae. The draft suggests that at least one year of followup be conducted on detachable balloon patients. The only detachable balloon currently in use in the U.S. is Interventional Therapeutics Corp.'s DSB product. During the June 11 meeting, the panel found that the existing clinical data for detachable balloons does not support safety and efficacy of the devices (see preceding story). FDA asked the panel to comment on how patient data should be stratified "for the purpose of analyzing scientific studies of the intracranial embolization balloon." The agency's guidance says that several medical conditions "are believed to have significant effect on outcome and therefore the data must be stratified and analyzed separately." Among the conditions listed are: "fistulas and aneurysms of the head and neck"; "pre-surgical management for hemorrhage control"; and "tumor therapy (other than pre- surgical)." Panel members disagreed on the necessity of stratifying data for analysis. Some felt that the rarity of conditions for which this therapy is applicable would lead to clinical study populations that are too small to partition; others felt the wide variation between conditions makes stratification necessary. Mark Wholey, MD, University of Pittsburgh, commented that although he liked the idea of stratification, it would be "very, very difficult to stratify that small a...patient population." Disagreeing with Wholey, Steven Piantadosi, PhD, MD, Johns Hopkins Oncology Center, Baltimore, said that he did not "see the disadvantage of stratifying. Stratifying is simply a technique to encourage balance between the treatment groups." FDA also asked, "What controls are needed, and feasible, for assuring valid scientific evidence of safety and effectiveness?" The agency's guidance would require "a comparison between a group treated with embolization and another, similar group that is treated by whatever therapy would otherwise be the best alternative." The document does not specify randomized, concurrent controls. Panel members again were divided on the issue of using randomized controls in light of the anticipated small size of the study population. Wilkinson asserted that with a small population, "it's not going to be a 'doable' study if you then require randomization of each patient. And so I would think the only way this kind of study is going to be done is with historic controls." Frank Yatsu, MD, University of Texas at Houston, however, argued that historical controls "are unacceptable because of the issues of contemporaneousness." He said that "many changes are going on in terms of current therapies," which make comparisons with historical controls "absolutely invalid."
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