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Pr Timothy Brighton: unprovoked venous thromboembolism

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MD-FM INSIGHT Tuesday 23 April 2013




Hello! You’re on MD-FM INSIGHT, the first web radio for e-Continuing Medical Education.

Clementine: Today we’re pleased to offer you a "question & answer" program devoted to the long-term management of unprovoked venous thromboembolism.

End of music


To find out about the most recent advances in this domain, we sat down with the senior author of the ASPIRE trial -- for “Aspirin to Prevent recurrent Venous Thromboembolism.” Dr. Timothy Brighton, from the Prince of Wales Hospital in Australia, led us through the details of the study.


So Dr. Brighton, before we go into the details of the study, can we back up a bit and start with some background on what led up to this study, in this particular patient population?

Bob-1-Brighton: There are three key points: the first is that there are a group of patients who develop an episode of, VTE or venous thromboembolism, DVT or PE for absolutely no reason –they hadn’t had a preceding operation or some sort of illness or leg injury or pregnancy or some explanation for the thombolism --It just comes out of the blue.  And so we call that group of patients, we consider them to have developed what we call “unprovoked thrombosis.” And so we know a little bit about that group of patients: We know that they have a very high risk of recurring thrombosis in the future, if they stop their anticoagulation treatment. So that’s the first point.

The second point is that we know that, if you keep warfarin going, it’s very effective at preventing this risk of recurring thrombosis, but a lot of people don’t want to take warfarin forever. After one episode of DVT or PE, they may not be able to take warfarin because of the risk of bleeding, or they may choose not to take warfarin in the long term. So… Prior to this study, we really didn’t have much evidence for any other approach and so because we know that aspirin does prevent the occurrence of venous thromboembolism in high risk surgical and medical patients, we thought ‘well why not try it in this group of patients to see if we can show that aspirin prevents recurrence in this group of patients.’ So that was the basis for doing this study.


OK that’s very clear –Thank you. So you wanted to test how well aspirin could prevent the occurrence of thromboembolism in this high-risk population. So tell us what you did:

Bob-2-Brighton: We recruited a bunch of patients who had unprovoked thrombosis, but after they finished their initial period of anticoagulation with heparin and warfarin, at a point in time, usually around about the 6 to 12 months mark, and said ok well why don’t we just compare aspirin in this patient group vs. placebo. They stopped their anticoagulation treatment, and they were randomized in a double-blinded study to received either low dose aspirin just 100 mg a day vs. a matching placebo. 


Ok… and the results?

Bob-3-Brighton: The results are complicated. The primary outcome of the study was recurrent venous thromboembolism. So that was recurrence of either leg vein thrombosis, lung clots or fatal pulmonary embolism. In the ASPIRE study, because we did not recruit the numbers of patients that we wished to recruit and there was a significant discontinuation rate of the study medication –it was a very long study –we were disadvantaged in terms of determining the effects of aspirin. We found a 26% relative risk reduction in recurrent vein thrombosis, but that was not statistically significant. But we did actually have 2 other important outcomes in the study: one was the prevention of vein thrombosis combined with other important vascular events, like myocardial infarction or stroke or sudden death, and in the ASPIRE study we found significant risk reduction for that endpoint of about 32%. And we also had another endpoint, which was sort of like an overall clinical benefit. So that took into account all the recurring vein thrombosis, all of the other important vascular events, bleeding and all causes of death. And we found a significant reduction in that endpoint, on aspirin, in our study.


So your study came out with some mixed findings... Is it still possible to draw an overall message from that?

Bob-4-Brighton: So I think.. There’s now 2 studies, of almost identical design, that have been published this year. Our study, which we are presenting and will be published shortly, and earlier this year the WARFASA study, from Italy, with which we collaborated with quite significantly. And so when you do a combined analysis of those two studies, I think the message is very clear: aspirin does reduce recurrent vein thrombosis in this group of patients, statistical significant reduction, as well as major vascular events and net clinical benefits. So it is an effective medication I think. But also it’s such a simple therapy, it’s widely available in the world, in all communities, at a low cost, it’s well tolerated. I think this is an important therapy, particularly in communities where these newer drugs are not going to be available to replace warfarin in the near future because of the cost. 


Ok so what’s the message for practitionners, should they put all patients who have suffered an unprovoked venous thromboembolism on aspirin after a short course of anticoagulants?

Bob-5-Brighton: It’s not for all patients. You know aspirin is not as effective as anticoagulation treatment, so for patients who want to continue anticoagulation treatment or we think should continue anticoagulation treatment --that is the most effective therapy for that group of patients. But you know there is a substantial proportion of people who are either unable to take for example warfarin forever, or who don’t wish to take anticoagulation for a long period of time because of the risks of bleeding, or of the inconvenience of treatment, and so now we have an option for that group of patients, not as effective, but I think nevertheless effective in its own way, better than taking nothing, which has been what has been the standard of care basically –no treatment, so I think aspirin has really an important role in that group of patients. 



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