Erich Minar says hopes for drug-eluting balloons are too high
Of late we can see a new hype in endovascular therapy concerning drug-eluting balloons.It is difficult to understand this enthusiasm given the very little experience and the few published data in the peripheral field.Until now, only short-term data (up to six months) in less than 100 patients have been published. Of course, there are some more data and a slightly longer follow-up in the coronaries, but, looking at the experience with drug-eluting stents, we have learnt that direct extrapolation from the coronaries to the peripheral vessels is not possible.Despite the very impressive data of coronary stenting with drug-eluting stents, the very few data with this technology in the femoropopliteal arteries have been rather disappointing.In my opinion, one of the main problems with drug-eluting stents in the peripheral vessels was the fact that some companies started clinical trials without sufficient experimental and preclinical data. This has led to a situation where, many years after starting the drug-eluting stents programme, we have no sufficient data and therefore cannot recommend the stents for use in the peripheral vessels.Looking at the situation with drug-eluting balloons, the same mistake looks set to occur again.Companies have started to sell drug-eluting balloons for use in below-the-knee arteries, without availability of clinical data in these vessels. With treatment of longer lesions – for example, in diabetics with critical limb ischaemia – it will become necessary to use more than one long balloon. Since we know that only a small portion of the drug reaches the vessel wall, there may be a problem with high systemic concentrations of a cytotoxic drug in patients with longer lesions.Of course we all hope that this technology will offer a solution for the as-yet unsolved problem of in-stent restenosis, but I think that it is urgently necessary to perform randomised studies before further use in the clinical routine.Despite the current promising short-term data concerning reduction of restenosis, I have some doubt that recurrence can be avoided in the long term.Restenosis that is caused by neointimal hyperplasia is a slow process, suggesting that the local administration of a drug would need to be prolonged in order to be beneficial. Using angioplasty balloons as drug carriers, the short-term drug exposure has to effectively suppress intimal proliferation in the long term.
Can this work?
The data in the SIROCCO-trial demonstrated a higher restenosis rate with a fast-release coating of the stent, and therefore the protocol was modified and in SIROCCO II only a slow-release stent was used.My own experience with inhibition of proliferation with endovascular brachytherapy, has left me with some doubts about such a long-term effect. Inhibition of clonogenic smooth muscle cells may delay the restenotic process, but may not avoid it.Therefore, we saw a late catch-up phenomenon, with an increased incidence of late restenoses – up to five years after endovascular brachytherapy.The clinician has to deal with the problem of a rather high percentage of restenoses after currently available endovascular techniques, especially in the femoropopliteal region, and he eagerly wants to get each new promising possibility as quickly as possible to reduce this restenosis rate.Of course the companies want to serve these demands, mainly for economic reasons.As working endovascular specialists, it is also our main task to definitively prove the effectiveness of any new concept through sufficiently large multicentre, randomised trials before recommending new methods for the clinical routine.
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