Does Aspirin Reduce Cancer Incidence and Mortality ?

Dr. Mangesh Thorat MBBS, MS(Surgery), DNB(Surgery), MNAMS Centre for Cancer Prevention Wolfson Institute of Preventive Medicine Barts & The London School of Medicine and Dentistry, London EC1M 6BQ Queen Mary University of Londonm Honorary Clinical Lecturer Division of Surgery and Interventional Science Whittington Hospital, LondonMedicalResearch.com Interview with:
Dr. Mangesh Thorat
MBBS, MS(Surgery), DNB(Surgery), MNAMS
Centre for Cancer Prevention
Wolfson Institute of Preventive Medicine
Barts & The London School of Medicine and Dentistry, London
Queen Mary University of Londonm Honorary Clinical Lecturer
Division of Surgery and Interventional Science Whittington Hospital, London

Medical Research: What are the main findings of the study?

Dr. Thorat : Accumulating evidence supports an effect of aspirin in reducing cancer incidence and mortality. Our analyses show that for average-risk individuals aged 50-65y taking aspirin for 10 years, there would be a relative reduction of between 7% (women) and 9% (men) in the number of cancer, myocardial infarction or stroke events over a 15 year period and an overall 4% relative reduction in all deaths over a 20 year period. The benefits of aspirin use would be most visible in the reduction in deaths due to cancer. If the findings of our study are applied to the UK general population aged 50-64 taking aspirin for next 10 years, on an average more than 6000 lives will be saved every year.

Medical Research: Why is your study different?

Dr. Thorat :The messages regarding prophylactic aspirin use in the past have been conflicting, primarily because

  • A thorough and systematic assessment of harms likely to be caused by aspirin at the level of general population was not done before. Lack of such assessment may have resulted in a perception that harms are excessive.
  • Previously, the harms were also grouped together, without giving a due attention to their severity. Some harms are frequent but have a low level of severity that cannot be equated to, for example, cancer or heart attack.
  • The effects on cancer, where the main benefit lies, were unappreciated or under-appreciated. This was largely due to the fact that the benefit is not apparent until after 3-5 years of follow up so early analyses did not see it.
  • The benefits were assessed only in a single disease/ single disease group, (e.g. cardiovascular disease or colorectal cancer) and not collectively in all diseases where aspirin has an effect.

With this study, we aimed to overcome these and other limitations of earlier studies. This is the first time

  • Both benefits and harms of aspirin were assessed together at the level of general population and
  • This assessment included all diseases aspirin has effect on, unlike previous studies where effect on single disease (e.g. heart disease) was assessed.

We also used most up to date evidence for effects on cancer, heart disease, bleeding etc and actual baseline rates of these various events in the general population.

Medical Research: What should clinicians and patients take away from your report?

Dr. Thorat : We are actually not talking about patients here; the results of our study apply to average-risk members of the general population.

An average middle-aged person (50-64 years of age) should consider taking aspirin and discuss this with their doctor (see figure below). Prophylactic aspirin at doses between 75 and 325 mg/d will be beneficial in such individuals if used for a minimum period of 5 years. As the risk of harms associated with aspirin rises steeply beyond 70 years of age, people older than 70 years of age should presently not consider taking aspirin.

Bleeding is the main harm associated with aspirin use. There are several risk factors for bleeding: diabetes, high blood pressure, obesity, smoking, alcohol consumption (especially at moderate or high levels) and H. pylori infection. Many of these are modifiable (e.g. smoking cessation, weight reduction, decreasing alcohol consumption) or treatable (e.g. H. pylori infection, high blood pressure). Additionally, aspirin is contraindicated in several circumstances. Therefore, a careful assessment and management of the risk of bleeding by a healthcare professional is essential before an informed decision regarding prophylactic aspirin use is made.

Figure: 1000 individuals aged 60 taking aspirin for 10 years, deaths over a 20-year period

Figure: 1000 individuals aged 60 taking aspirin for 10 years, deaths over a 20-year period


Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Thorat : There are some unanswered questions, especially regarding the optimum dose and duration of aspirin use. All the net benefits we assessed were based on use of low-dose aspirin. The net benefits could be larger (or even smaller) when larger doses are used since clinical and laboratory studies point to a potential to achieve a greater benefit with higher doses. Aspirin, like other cancer preventive drugs (e.g. tamoxifen), has a carry-over effect; i.e. the beneficial effects continue even after the use is stopped. However, the exact extent of this carry-over effect is not known. If the carry-over effect is very long, use for 5 years may accrue considerable benefit; if not; longer use (e.g. 10 years) may provide greater net benefit. Both these, dose and duration, questions need to be addressed in a randomised trial to determine optimum dose and duration of aspirin use. Additionally, H. pylori infection is responsible for a significant proportion of stomach bleeding and ulcers events. The value of screening and eradication of H. pylori infection before starting aspirin also needs to be appraised since the prevalence of this infection is changing.

Citation:

Estimates of benefits and harms of prophylactic use of aspirin in the general population.

J. Cuzick, M. A. Thorat, C. Bosetti, P. H. Brown, J. Burn, N. R. Cook, L. G. Ford, E. J. Jacobs, J. A. Jankowski, C. La Vecchia, M. Law, F. Meyskens, P. M. Rothwell, H. J. Senn, and A. Umar

Ann Oncol first published online August 5, 2014 doi:10.1093/annonc/mdu225