Clinical Topics & News

Cancer Prevention and Gastrointestinal Risk

Although low-dose aspirin is used for colorectal cancer and vascular prevention, researchers analyze the risk of gastrointestinal bleeding attributable to frequency of treatment.


Low-dose aspirin is recommended to help prevent colorectal cancer and vascular disease as well as to reduce mortality. Research suggests that low-dose aspirin also can be useful as an adjunct treatment in established cancers. The potential, however, is offset by concerns about bleeding.

Are the concerns valid? When gauging the risks vs benefits of aspirin for patients at risk for bleeding, considering not only the severity of events, but also the frequency is important, say researchers from Cardiff University, Hywel Dda University, University of Cambridge, Harvard, University of Zaragoza, University of South Wales, Swansea University, National University of Singapore, and University of Leicester.

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They point out that most estimates of harm from aspirin are based on the frequency of “major” gastrointestinal (GI) bleeding together with cerebral bleeding. But they also note that although GI bleeds can be severe, they’re “acute events usually followed by recovery without sequelae.” Strokes, on the other hand, can have lasting effects in survivors; and people who survive heart attacks or cancer may require complex and lifelong interventions.

The researchers suggest weighing the risk of fatal bleeds attributable to aspirin with the severity of the disease events prevented. And the distinction between GI bleeding and fatal bleeding isn’t trivial, they contend. Studies have already shown that the risk of death from aspirin-related GI bleeds is lower than that of spontaneous GI bleeding.

To put the discussion on a more even footing, the research team looked at 11 long-term, randomized controlled trials of aspirin prophylaxis with data on fatal adverse effects (AEs). They also incorporated new data from direct e-mail contact with the authors of some of the studies.

They found that although aspirin increases the risk of GI bleeding by about 60%, low-dose aspirin is associated with a lower risk of fatality among the patients who develop GI bleeding. The researchers note that no report mentioned the use of gastric protection by proton pump inhibitor or other treatment.

Most important, the researchers say, is the finding that among all the subjects who were taking aspirin, there was no increase in death from GI bleeding compared with those randomized to take no aspirin.

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Also important, they add, is to bear in mind the duration of aspirin taking. Almost all studies of cancer prevention, they note, show a 3- to 5-year delay before the benefits of aspirin are clinically apparent (because the effects on cells take a while to show up, that is, as the absence of a tumor).

However, the incidence of GI bleeding attributable to aspirin seems to drop over time: Within the first month of aspirin taking, the risk increases more than 4-fold, but then declines rapidly. After about 3 to 5 years of taking aspirin, there seems to be no excess in GI bleeds. Similarly, most deaths from bleeding happen with the first month, implying underlying untreated gastric pathology, the researchers say.

GI bleeds are still the majority of the AEs caused by aspirin, but thanks to better treatments, GI bleeding and fatal bleeding have declined as much as 20% to 50% in some countries, such as Scotland, Spain, U.S., and Wales. In the risk-benefit analysis, however, the researchers say, the “undesirable effect” of prophylactic aspirin as serious as a vascular event or cancer is rare: Low-dose aspirin is associated with 1 death and 1 disabling hemorrhagic stroke per year in every 10,000 people, and that number could be lower if hypertension is treated adequately.


Recommended Reading

Colorectal Carcinoma and Emerging Targeted Therapies
The Importance of Lymph Node Retrieval and Lymph Node Ratio in Male Patients With Colorectal Cancer: A 5-Year Retrospective Single Institution Study
Colorectal Cancer Statistics Among Patients Reported in the Veterans Affairs Central Cancer Registry
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Patterns in the Use of Neoadjuvant and Adjuvant Therapy in Stage II/III Rectal Cancer and Associated Survival
Stage IV Rectal Cancer Trends by Year: A Review of the National Cancer Database, 1998 to 2009
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Colorectal Screening: Available but Underused
Strollin’ the Colon: A Collaborated Effort to Provide Education and Screening Outreach for the Improvement of Awareness, Access, and Early Detection of Colorectal Cancer
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