Although there is no certainty, there is growing evidence which suggests that if aspirin is given to patients with cancer, there is a reduction in the spread of the cancer, and an increase in survival. The evidence is not conclusive, but it is highly suggestive for bowel cancer (1-4), less so for breast (5-7) and prostate (8-10). For other cancers the evidence is too sparse to make a judgement about possible benefit. It has also been pointed out in studies of the prevention of cancer, an early effect on metastatic spread implies a probably treatment effect of aspirin.(11)

In fact, since about 1960 a number of research workers have pointed out that the effects of aspirin on certain biological mechanisms justify an expectation of benefit to patients with cancer.[12-14] Thus, aspirin can interrupt tumour growth and reduce metastatic spread, it inhibits the development of new blood vessles, it enhancements enhances both DNA mismatch repair and cellular death (apoptosis) and it can enhance improve the response to chemotherapy. Benefit from treatment with aspirin is therefore not unexpected.

A number of large, long-term studies are being set up at present, and in five or ten years there will be a lot more evidence about whether or not aspirin is helpful in the treatment of some cancers.