When in comes to cholesterol levels, the mantra is usually ‘the lower the better’. The idea here is that the lower the level of cholesterol in our bloodstreams, the lower our risk of cardiovascular disease (e.g. heart attack and stroke) and therefore, we hope, death from these conditions. But wait a minute, even if this were true, how about if lower levels of cholesterol actually increased our risk of other important conditions? Might an increased risk of, say, cancer, offset any apparent advantages of low cholesterol with regard to cardiovascular disease.
This is not just theory: evidence shows that the lower cholesterol levels are, generally speaking, the higher the risk of cancer. The most recent study to show this association was published this week in the Journal of the American College of Cardiologists (JACC). The study was designed to assess the risk of cancer in individuals taking statin (cholesterol-lowering drugs). In this study, the results of 15 statin studies were assessed.
The researchers found, as had been noted before, that in individuals in these studies taking placebo, the lower their cholesterol levels, the higher their risk of cancer. They also found the same thing in individuals taking statins in these studies. But, for a given cholesterol level, statin takers were, overall, not found to be at an increased risk of cancer compared to those taking placebo.
This study led to proclamations in the press that statins do not cause cancer. And that might be true. But it might not be true too.
Let’s imagine for a moment that low cholesterol levels are not just associated with cancer but actually cause cancer. And let’s imagine that through their cholesterol-reducing capacity statins can therefore enhance cancer risk. Well, it likely takes some time for statins to reduce cholesterol and almost certain even longer for that to manifest as full-blown, diagnosable cancer. In other words, the statin trials may simply not have gone on long enough for the long-terms effects on cancer to be properly assessed.
Looking at individual studies within the review we find that some studies show no statistically significant increased risk of cancer in statin takers. Some studies even showed a reduced risk of cancer. But, and this is important I think, some individuals studies did show an increased risk of cancer in those taking statins. The results of these studies can of course be diluted by the other studies, but they are still there, and some would argue that their presence casts a pretty ominous shadow over statin and perhaps cholesterol-reducing therapy generally. The authors of an accompanying editorial in the same edition of JACC point out that the results of the review are not definitive, and don’t prove that reducing cholesterol levels down to low levels is safe as far as cancer is concerned.
Not so long ago I reported on a study (the so-called SEAS study) which found that treatment with two cholesterol reducing drugs led to an increased risk of cancer compared to placebo. As even the authors of the JACC review conclude, further studies of longer duration are needed to assess the risk of cholesterol reducing medicine with regard to cancer risk.
References
Alawi A, et al. Statins, Low-Density Lipoprotein Cholesterol, and Risk of Cancer. Journal of the American College of Cardiologists. Published on-line 20th August 2008.
So it sounds like what the study showed is that statins don’t cause cancer independently of their cholesterol-lowering effect. But they still lower cholesterol, which associates with cancer risk in placebo and statin-takers. My interpretation of these data is that statins DO cause cancer.
You correctly point out that studies in many sciences imcluding medicine are too short term. The pinciple of research needs an overhaul,questions such as how do we integrate short term studies with long term goals need careful study and answer. Highly publicized studies grab headlines and may mislead. Let us not be apologizing that our results are based on short term studies and may not really properly diagniose the real facts.
The West Midlands Centre for Adverse Drug Reactions have recently produced a bulletin about the possible cancer risks of Vytorin over and above its lack of efficacy in reducing the risk of cardiovascular events.
http://adr.org.uk/?p=163
It is interesting to note that our old friend pharmacovigilant pharmacist Dr Anthony R Cox is a senior staff member at adr.org.uk. His very own black triangular blogsite …
http://www.blacktriangle.org/blog/
… has been very quiet of late but his miniblog highlighted the ADR centre’s Vytorin report with the words,
“Cancer risk with Simvastatin and Ezetimibe? Jury still out. Don’t panic. I await the Daily Mail with baited breath!”