BACKGROUND: Colorectal cancer (CRC) is one of the most common cancers in the 
developed world and is the second leading cause of cancer-related mortality in 
the UK and USA. Regular use of aspirin can reduce cancer incidence, recurrence, 
metastasis and cancer-related mortality.
SOURCES OF DATA: Peer-reviewed journals, governmental and professional society 
publications.
AREAS OF AGREEMENT: There is a wide body of evidence from observational studies 
and randomized trials that aspirin reduces risk of CRC. There is a delay of 
several years between initiation and effect. There is interpersonal variation in 
aspirin metabolism but pharmacogenetic testing is not yet sufficiently sensitive 
or specific to justify routine use.
AREAS OF DISAGREEMENT: There is uncertainty about the optimal dose and the 
duration of aspirin. There is debate around use for the general population but 
there is growing consensus on use in those at increased risk of developing 
cancer.
GROWING POINTS: Understanding is growing of the possible mechanisms by which 
aspirin exerts its anticancer effects. Large-scale meta-analyses are quantifying 
the cost-benefit ratio in the general population. International trials are 
underway to assess the optimal dose in high-risk individuals and the role of 
aspirin as an adjuvant in those who present with a malignancy.