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There has been increasing interest in the role of aspirin in reducing the risk of colonic polyp formation and also reducing the incidence of colorectal cancer. A number of recent studies have once again addressed this issue.

A recent large-scale retrospective study from Hong Kong suggested that long-term use of aspirin was associated with a 25% reduction in the incidence of colorectal cancer and a 41% reduction in risk for colorectal cancer mortality.

The study of more than 600,000 people in Hong Kong divided patients into those that had been prescribed aspirin for more than six months (204,179) and those that were not taking aspirin (408,399). The average length of time that individuals was taking aspirin was 7.1 years. Patients were followed up for 14 years or until the time of their death.

Those in the aspirin group had a significantly lower incidence of colorectal cancer (2.51% versus 3.27% or, 0.76:95% CI, 0.74 – 0.79) and the mortality related to colorectal cancer (1.02% versus 1.7%; 0.59; CI, 0.56 – 0.62). The incidence of colorectal cancer started to decline after eight years of use and there was an inverse relationship between the duration of use and the incidence of colorectal cancer.

As expected there was higher incidence of gastrointestinal bleeding in patients taking aspirin (4.64% versus 2.74%) and aspirin use marginally increase the risk of mortality related to gastrointestinal bleeding (your .4% versus 0.36%). However, patients who are giving gastro protection in the form of a proton pump inhibitor or H2 antagonists had a significantly lower incidence of gastrointestinal bleeding compares the dolts who did not take gastro protection.

The authors concluded that long-term use of aspirin is used both the incidence and mortality of rectal cancer but had a negative impact on the incidence and mortality related to gastrointestinal bleeding. The risk of bleeding however can be reduced by the use of either a proton pump inhibitor or H2 antagonists (Tsoi 2018).

Another recent study (García Rodríguez 2017) compared cancer-free individuals who were new (n=170,336) or non-users of LDA (n=170,336). The results suggested that the risk for developing colorectal cancer was reduced by 34% in patients initiating treatment with low dose aspirin, irrespective of sex (RR=0.66, 95% CI: 0.6 – 0.74). The reduction in risk is apparent across all ages and is unrelated to the dose. Starting low-dose aspirin therapy reduced risk of stages B, C & D rectal cancer which suggests that low-dose aspirin may also have an impact in slowing the progression of established colorectal cancer. There was also a suggestion that low-dose aspirin therapy of five years or more years is associated with a substantial reduction in the risk of early colorectal cancer colorectal risk (RR for Dukes Stage A CRC was 0.53 (0.24-1.19).

A number of other studies have looked at the association between the use of aspirin and the risk of a variety of cancers. A recent large-scale meta-analysis of observational studies concluded that aspirin use is associated reduction the risk of gastric, oesophageal, colorectal, pancreatic, ovarian, endometrial, breast, prostate, small intestine cancers and neuroendocrine tumours cancers (Qiao 2018).

A total of 218 studies and 309 reports were included in the meta-analysis. There was an overall significant reduction in the risk of cancer (RR = 0.89, 95% CI: 0.87 – 0.91), and gastric (RR = 0.75, 95% CI: 0.65 – 0.86), oesophageal (RR = 0.75, 95 CI: 0.62 – 0.89 close bracket, colorectal (RR = 0.79, 95% CI: 0.74 – 0.85), pancreatic (RR = 0.80, 95% CI: 0.68 – 0.93), ovarian (RR = 0.89, 95% CI: 0.83 – 0.95), endometrial (RR = .92, 95% CI: 0.85 – 0.99), breast (RR = 0.92, 95% CI: 0.88 – 0.96) and prostate (RR = 0.94, 95% CI: 0.90 – 0.99) cancers.

These studies add to the growing list of papers that have reported on the beneficial effect of aspirin in reducing the incidence and mortality of colorectal and other cancers. Using gastro protection in the form of a PPI or H2 antagonist also reduces the incidence of GI side-effects.

References

Tsoi KKF, Chan FCH, Hirai HW et al. Risk of Gastrointestinal Bleeding and Benefit from Colorectal Cancer Reduction from Long-term Use of Low Dose Aspirin. A Retrospective Study of 612,509 Patients. J Gastroenterol Hepatol. 2018 Apr 17. doi: 10.1111/jgh.14261.

García Rodríguez LA, Soriano-Gabarró M, Bromley S et al. New use of low-dose aspirin and risk of colorectal cancer by stage at diagnosis: a nested case-control study in UK general practice. BMC Cancer. 2017 Sep 7;17(1):637. doi: 10.1186/s12885-017-3594-9.

Qiao Y, Yang T, Gan Y, et al. Associations between aspirin use and the risk of cancers: a meta-analysis of observational studies. BMC Cancer. 2018 Mar 13;18(1):288. doi: 10.1186/s12885-018-4156-5.

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