Wednesday, 8 December 2010
Aspirin and Cancer, Will it Help?
So, what is Aspirin? Not a silly question because it has many uses, and is in fact the most prescribed (mainly self prescribed), medicine in the world.
It is an analgesic, so eliminates or reduces pain, usually mild pain. It is also classified as an NSAID, so it is a non-steroidal anti-inflammatory drug, because it's primary mechanism is to inhibit cyclo-oxygenase products in the body (inflammatory agents like prostaglandins). It also has antipyretic properties (reduces fever). In recent years it has been used at low doses as an anti-platelet agent (it 'thins' the blood) in the treatment and prevention of CHD and CVD. Pretty useful then it might seem, but it has been linked to gastro-intestinal and stomach bleeding and is contra indicated for hemorrhagic stroke, all due to this last mechanism.
Patented in 1897 by Bayer, as the synthetic form of the original white willow bark extract, it is acteylsalisylic acid (C9H804), it's patent has long expired but Aspirin as opposed to aspirin, is still a Bayer patent nonetheless. It has been an OTC (over the counter) medicine since 1915. The world uses about 35,000 tonnes of the stuff every year, so despite its low cost, it still turns a dollar for the generic pharmaceutical companies. It should not be given to children, because it can cause Reye's Syndrome which is potentially fatal and is only used for the treatment of Kawasaki Disease, which has nothing to do, with the penchant for riding motor cycles at an early age, but another problem altogether, or for certain types of post operative care, for which it is a useful product, to prevent DVT (deep vein thrombosis). Throughout its long life it has been over and under used, and recently used almost only for heart disease prevention. Many foolishly, I feel, self prescribe it for this purpose, to their cost, as long term use can cause ulcers. Before the widespread use of Acetaminophen (Paracetamol) and Ibuprofen, (when I was young), it was the only analgesic available over the counter. Except of course for Codiene, which was then widely available over the counter; now stopped of course due the possible addiction problems of opiates.
Cutting to the chase, what then is the 'break through' in its use that causes it to be hailed as a cheap and simple Cancer drug?
Well yesterday, the Lancet published details of a study (of studies), undertaken over some twenty years, of the use of aspirin as opposed to a placebo, originally for the prevention of heart disease. This meta-analysis highlights the preventative effect of aspirin for a number of Cancers, but the effect was not apparent for at least five years or even longer for colon, rectal or prostrate cancers. The effect seemed to be better the longer it was taken and the older you were. However, a number of quite large reductions in risk are quoted for this cohort (the one studied) of some 25,000 or so, for various cancers. I have reservations however, as the implied rather than actual, reductions are somewhat lower than described. Relative risk being used, rather than absolute. This paper provides a better explanation of the research involved. The abstract url I have given for the study is in fact pretty brief, and as usual, despite it's importance, one has to pay a fee, both to access all the data, and even more to publish it. Let not medicine, and science, miss an opportunity to make a few quid (bucks) extra, even when we have paid for the research, probably the Institution doing it, and the wages of those involved.
One thing stands out, and that is the length of time you need to take this drug before protection is afforded; between five and seven years. The reduction in 'absolute' risk is also quite minimal too; with a 2% reduction in the twenty year risk for colorectal cancer, from 3.5% to 1.5%. Overall life time risk for this Cancer is in the order of 5%.
I personally view the enthusiasm with which this was greeted with some alarm. It is being sold as a 'get out of jail free card' for humans, so they can go forward without changing their lifestyle. That's pretty much the same concept, as taking statin's if you're healthy. Lets medicate everyone, in the hope we'll catch all. Every time we've done this in the past things have gone badly wrong. You used to see bumper stickers in the US, that said " Kill em all and let God sort it out". Well it's the same mindset. Not one I aspire to.
The other problem, and this is true of all meta-analyses, is which of the many studies to include, to ensure there are no paradoxes or selection bias ( such as Simpson's Paradox ).They do have some strengths, but without more reference data to examine it is a little difficult to afford it the credibility of a long term, double blind placebo trial, which may have been too expensive or may have thrown up ethical problems. Also, the usual caveat has to apply; this study is observational and 'observation does not prove causation'. And finally, much has been made recently of 'what the placebo actually chosen is'. If, for instance one included as a placebo, in a trial of diabetic hypoglycemic agents, the obvious thing we believe placebo's to be; a 'sugar pill', we would for sure, get good results for the drug on trial. Although I'm certain that no Pharma company would stoop so low. Well reasonably certain; well maybe there's doubt. Thing is, we simply don't know.
There are plenty of other steps we can all take to limit our risks for Cancer, most of which relate to lifestyle and diet (see my many previous posts) and frankly, they are likely to lower risk, far more than the use of aspirin. But, if you have a family history of Cancer especially bowel cancer, then look at the risks. Maybe it would be worth it, for someone with a robust gastro-intestinal system and no history of problems, such as ulcers, IBS, gastritis etc.
Aspirin is a fairly simple chemical medicine, and I do applaud the use of simple solutions to complex health problems, because there are plenty out there. I have considerable doubt however, that this is one to adopt universally. There are many more, even simpler that work. I will write about these soon.