In 2010 papers in the British Medical Journal (BMJ) and the Lancet showed long-term aspirin use to be the most protective cancer drug yet found. So why are we not all being prescribed aspirin?
Aspirin is commonly used to relieve minor aches and pains and to reduce fevers. Its active ingredient, Salicylic acid, has been used since antiquity in the form of willow bark. In the 1800s a series of chemists synthesized this ingredient from the bark of the willow tree. In 1897 Felix Hoffmann, working for Bayer AH, produced a synthetically altered version that caused less digestive upset and called it aspirin.
Towards the end of the 20th century trials showed that aspirin had cardio-protective effects which are now well documented. Aspirin is now commonly used to protect against heart attacks and strokes in subsections of the population which are deemed at high risk of heart disease/problems. A recent survey in Caerphilly, South Wales, reported that 25% of healthy subjects aged over 50 with no previous vascular event stated that they take aspirin regularly to protect their hearts, and data from the USA indicate that the rates there are even higher. However, aspirin is not without side effects - it can cause severe cerebral and gastrointestinal bleeding and gastrointestinal ulcers. Because of this aspirin is not recommended by health authorities as a drug everyone should be taking on a daily basis.
New research however has shown that taking aspirin may help prevent cancer and this may alter the delicate balance between benefit and risk.
In March 2010 the Journal of Clinical Oncology published an article which showed that among women living at least one year after a breast cancer diagnosis, aspirin use was associated with a decreased risk of recurrence and breast cancer death. This was then followed by an article in the Lancet (abstract here) which used a review of 8 randomized trials, totaling 25,570 patients and 674 cancer deaths. The researchers showed that after using aspirin the death rate due to cancer was reduced by 21%. When individual patient data were analyzed it was shown that the benefit was apparent only after 5 years of follow up for esophageal, pancreatic, brain and lung cancer, and longer for stomach, colorectal and prostate cancer, but that the benefit lasted for at least 20 years. The benefit was unrelated to sex, smoking or dose of aspirin (over 75mg), but did increase with age.
This means that for those who took aspirin for 5 years aged 55-64 years, 20 years later, one cancer related death would be prevented for every 22 people who took aspirin. However for those aged 65 years and older, one cancer related death would be prevented for every 14 people taking aspirin. Whilst this may not seem like a massive improvement on the individual scale, as a public health benefit it is highly significant.
Tom Meade of the London School of Hygiene & Tropical Medicine said that the findings are likely to “alter clinical and public health advice because the balance between benefit and gastrointestinal bleeding has probably been altered towards using it”. However he warned, as do other health bodies, that just because aspirin is a non-prescription drug it does not mean that people should assume it has only small effects.
Gastrointestinal bleeding is clearly an important side-effect of aspirin. But whatever the frequency of bleeding its seriousness does not match that of the diseases aspirin can prevent. In addition a bleed is not associated with other long-term conditions which often accompany vascular disease or cancer which make a sufferer’s life difficult. The bleeds caused by aspirin are not serious bleeds and there is no evidence that aspirin has lead to a greater number of deaths from bleeding. Furthermore there are drugs which could also be taken in conjunction with aspirin to reduce the risk of bleeding. Conversely, the increased risk of a cerebral bleed attributable to aspirin cannot be prevented, nor predicted. Although the increased risk is very small, it is severe and the greatest problem with aspirin.
33% and 29% of deaths in the UK in 2009 were due to vascular disease and cancer respectively. It is important therefore to consider how a drug which is already widely available to the public and reduces both can fit into the current healthcare framework. People need to be given advice about aspirin as a preventative measure so they can make an informed decision within the context of other protective health care behaviours such as non-smoking, exercise, moderate drinking and dietary changes.