The role of aspirin in preventing colorectal cancer.

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.