Thrombosis Risk Does Not Translate to Major Events
Data must be seen in the context of the overall benefits associated with drug-eluting stents.
Although several recent trials indicate that there may be an increased risk of thrombosis associated with drug-eluting stents, this excess risk is relatively low, according to Stewart J. Pocock, PhD, Professor of Medical Statistics at the London School of Hygiene and Tropical Medicine in England.
Pocock, speaking at yesterday’s roundtable discussion regarding the trials that examined drug-eluting stents, said both doctors and patients need to also consider the benefits. “I have tried to convey that from the data available, there does appear to be an excess risk of thrombosis,” Pocock said. “But this risk is relatively low and needs to be seen in the context of the overall benefits of drug-eluting stents.”
Pocock said in medical research, smaller studies usually gain attention first but larger meta-analyses are more valuable for understanding data.
Analyses
The meta-analysis of the Cypher stent (Cordis/Johnson & Johnson) indicated that after one year, five patients treated with a Cypher stent and no patients treated with a bare-metal stent experienced late thrombosis. In the meta-analysis of the Taxus stent (Boston Scientific), which followed patients beyond one year, nine patients treated with a Taxus stent and two patients treated with a bare-metal stent experienced late thrombosis. “Five vs. zero and nine vs. two: both are borderline significant, with a P value of about .05,” Pocock said. “Put them together and it’s 14 vs. two. Now it is overwhelmingly significant, with a P value of .01.”
But Pocock said the data require further examination. He said the data indicate that there is an excess risk, and it is highly significant. “But then you need to see it from a patient perspective to understand what the absolute risk is,” he said. “And the absolute risk is about 1.8 events per 1,000 patient years. This is roughly one event per 500 patient years of follow up. So the absolute risk is small.”
In context
Pocock said the data should be viewed in the context of the overall patient and the risk of other events. “When viewed in this context, there was no overall increased risk of death or myocardial infarction in either dataset,” Pocock said. “Therefore, the late stent thrombosis problem is not translating into an overall patient risk problem of major events.”
Pocock also noted that all medical treatments have a safety risk; doctors and patients need to always consider this safety risk in the context of the overall benefit of the treatment. “There are major benefits with drug-eluting stents in terms of target lesion revascularization and avoiding the need for surgery,” Pocock said. “Those translate into improvements in quality of life for the patient.”