Friday, November 9, 2012

Do statins really reduce the risk of cancer? - Briffa

Yesterday saw the on-line publication of a study in the New England Journal of Medicine (NEJM) that concerns statins and is getting more than its fair share of media attention. The study, conducted in Denmark, analysed the rates of death from cancer in individuals taking statins, and compared them to those in individuals not taking these drugs. Those taking statins were found to be at a statistically significant reduced risk of dying from cancer. Some seem keen to claim that statins may not only be an answer to heart disease, but our cancer woes too. Take this headline for example which you can find here: ‘Statins cut mortality in cancer patients’. The wording of this title on a website dedicated to the education of doctors strongly suggests that statins actually reduce the risk of death from cancer.

But, not so fast. The NEJM study is what is known as ‘epidemiological’ or ‘observational’ study. The study tells us that statin use is associated with a reduced risk of death from cancer, but it can’t tell us whether or not statins actually cut cancer risk.

One fundamental problem with studies of this nature is that they are subject to what is known as the ‘healthy user effect’. Basically, what this means is that healthier, often more health-conscious individuals are more likely to end up on statins than less healthy, not so health-conscious individuals. Because of this, it’s possible that the apparent benefits of statins with regard to cancer (or anything else) are not to do with the drugs themselves, but the health characteristics of those more likely to take statins.

If we really want to know if statins reduce the risk of cancer death then we need to look to what are known as ‘intervention studies’ in which, usually, roughly equivalent groups of individuals are given statins or placebo. These studies, the gold standard of which are ‘randomised controlled trials’ do have the potential of discerning the true effects of drugs and other treatments.

Single studies such as these can provide useful data, but sometimes it makes sense to amass data from several studies to get a decent overview of the impact of a drug or class of drugs. Such grouping of studies together are referred to as ‘meta-analyses’.

One meta-analysis published in 2009 found that statin use was not associated with a reduced risk of cancer [2]. A more recent meta-analysis published this year found the same thing [3]. Meta-analyses of intervention studies are not perfect, but they are much better than (crappy) single epidemiological studies like the one currently doing the rounds. And it’s perhaps worth bearing in mind that there as been at least some concern about the impact statins might have on cancer risk in the elderly. In one study, statin use (compared to placebo) increased the risk of cancer by 25 per cent (statistically significant) [4].

Put in this context, the frothing enthusiasm exhibited by some regarding this latest study seems inappropriate. And for a website dedicated to the education of doctors to proclaim that ‘Statins cut mortality in cancer patients’ is downright negligent.

1. Nielsen SF, et al. Statin Use and Reduced Cancer-Related Mortality. NEJM published online 8 October 2012
2. Brugts JJ, et al. The benefits of statins in people without established cardiovascular disease but with cardiovascular risk factors: meta-analysis of randomised controlled trials. BMJ 2009;338:b2376.
3. Cholesterol treatment trialists’ collaboraton. Lack of effect of lowering LDL cholesterol on cancer: meta-analysis of individual data from 175,000 people in 27 randomised trials of statin therapy. PLoS One 2012;7(1):e29849. Epub 2012 Jan 19.
4. Shepherd J, et al. Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial. Lancet 2002;360(9346):1623-30
Read the complete article here.

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