(HealthDay News) — Regular aspirin use is associated with a lower long-term risk of colorectal and other, particularly gastrointestinal, cancers as well as a reduced risk of distant metastasis, according to research published online March 21 in The Lancet Oncology.

Annemijn M. Algra and Peter M. Rothwell, F.Med.Sci., of the University of Oxford in the United Kingdom, conducted a systematic review and meta-analysis of cohort and case-control studies published from 1950 to 2011 and stratified by frequency, dose, and duration of aspirin use. Results from observational studies regarding the effect of aspirin on 20-year cancer mortality and risk of metastasis were compared with results from randomized controlled trials.

Using data from case-control studies, the researchers found that regular aspirin use reduced the risk of colorectal cancer by 38 percent, and 20-year colorectal cancer mortality by 42 percent. Similar results were observed for other gastrointestinal cancers, including esophageal, gastric, and biliary, as well as breast cancer. Using data from cohort studies and adjusting for baseline characteristics, cancer stage, and duration and frequency of aspirin use, regular use of aspirin was associated with 31 percent fewer cancers with distant metastases; however, regular use did not seem to affect regional spread. Randomized trial results correlated well with those from observational studies.

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“Observational studies show that regular use of aspirin reduces the long-term risk of several cancers and the risk of distant metastasis. Results of methodologically rigorous studies are consistent with those obtained from randomized controlled trials, but sensitivity is particularly dependent on appropriately detailed recording and analysis of aspirin use,” the authors write.

Rothwell disclosed financial relationships with pharmaceutical companies with an interest in antiplatelet agents, including AstraZeneca, Bayer, Boehringer Ingelheim, Sanofi-BMS, and Servier.

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