Short-term effects of daily aspirin on cancer incidence, mortality and non-vascular death: analysis of the time course of risks and benefits in 51 randomised controlled trials

Overview

To better characterize the effects of aspirin therapy on cancer prevention, the authors of this article evaluated the occurrence of cancer, cancer deaths and non-vascular deaths in 51 randomized trials of daily aspirin. They found that aspirin reduced the risk of cancer deaths. This benefit was most significant with five years of aspirin treatment.

Methodology

The 51 randomized trials were published between 1974 and 2011 involving 40,269 participants. This meta-analysis sought to combine data from multiple studies, in order to aggregate enough patient experience to be able to make specific conclusions about cancer risk. The authors evaluated endpoints of cancer deaths and non-vascular deaths, as well as the timing of the aspirin effect. In the combined analysis, aspirin was provided in doses varying from 100 mg every other day to 500 mg once a day.

Results

  • Aspirin reduced the risk of non-vascular death, avoiding 152 deaths among the 40,269 patients who took aspirin (the number of persons needed to treat is 265 to avoid one death).

  • Of the trials that evaluated specific cancers by location in the body, aspirin appeared to reduce deaths from colorectal cancer and lymphoma.

  • There was a trend towards a reduced risk of female reproductive cancers (e.g., ovarian, cervical cancer), but this finding could have been due to simple random chance.

  • Most of the benefit occurred after five years of aspirin treatment, but there was some mortality benefit even during the first three years of treatment.

  • After three years of treatment, the incidence of cancer was reduced by about 25% in patients who took aspirin, independent of age, sex and smoking status.

Conclusions

  • Aspirin is associated with a decreased incidence of cancer. The analysis suggests that daily aspirin use is associated with a decreased incidence of cancer and a decreased risk of dying from cancer. The benefits are most pronounced in patients who take aspirin for at least three years, but present even in patients taking aspirin for less time. This benefit was most significant with five years of aspirin treatment.

  • Increasing evidence exists that aspirin prevents colorectal cancer and cancer-related deaths. There is increasing evidence that aspirin prevents colorectal cancer and cancer-related deaths, especially in patients who have taken aspirin for more than five years. Most of this data has come from clinical trials of patients taking aspirin to prevent cardiovascular disease, and there are few trials designed to look specifically at aspirin’s effects on cancer prevention.

  • Greatest benefit of aspirin therapy was after five years of treatment. Most of the benefit of aspirin in cancer prevention occurred after five years of treatment, but there was some mortality benefit even during the first three years of treatment. After three years of treatment, the incidence of cancer (in aggregate) was reduced by about 25% in patients who took aspirin, independent of age, sex and smoking status.

  • The reduction of cancer risk should be considered when discussing aspirin use with patients.