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Colorectal Polyps and Cancer and the Benefits of Aspirin Therapy
- Colorectal cancer is cancer that occurs in the colon or rectum. It is often
referred to as colon cancer. The colon is the large intestine or large
bowel. Most colorectal cancers develop first as colorectal polyps, which are
growths inside the colon or rectum that may later become cancerous.
- Colorectal cancer is the second leading cause of cancer death in the US.It
affects men and women equally and risk increases with age.
[i]
- Not counting skin cancers, colorectal cancer is the third most common cancer
found in men and women in this country. The risk of a person having colorectal
cancer in their lifetime is about 1 in 19.
[ii]
- There were approximately
150,000 new cases and 50,000 colorectal cancer-related deaths in the
United States last year.
[iii]
- Colonoscopy is regarded
as the gold standard in colorectal cancer screening. There are an estimated
14 million colonoscopies in the United States
each year. Adenomas (a type of polyp) are found in approximately 25%
of screening colonoscopies, and in more than 40% of colonoscopies for prior
adenomas.
Aspirin to Prevent Colorectal Cancer
- Over the past 30 years,
compelling data have emerged suggesting that aspirin can suppress carcinogenesis
(the creation of cancer) in the large bowel.
[iv]
-
Aspirin blocks the Cox-2
enzyme, which is thought to play a role in the development of colon polyps and
their transformation to colon cancer. The Cox-2 enzyme promotes inflammation
and cell proliferation. Colorectal cancers over-express this enzyme.
[v]
- A combined analysis of four separate, government-funded randomized controlled
trials concluded that aspirin is of benefit in the prevention of colon polyps,
the precursor to colon cancer.
- A consensus statement
resulting from the 5th International Conference on Cancer Prevention
(2008) stated that aspirin clearly shows a chemopreventive (the use of natural
or synthetic compounds to prevent cancer development or progression) effect
on colorectal cancer and likely other cancer types, as well.
[vi]
-
Recent analysis of the
Nurses' Health Study and the Health Professionals Follow-up Study
concluded that regular use of aspirin after the diagnosis of colorectal cancer
was associated with a significant reduction in risk of colorectal cancer mortality.
[vii]
Aspirin and the Risk of Upper Gastrointestinal Bleeding
-
Although
the benefits of aspirin in colorectal neoplasia (adenomatous polyps and cancer)
are well documented, the long term use of aspirin is associated with the clinically
important risk of upper gastrointestinal bleeding (UGIB). The use of
aspirin is associated with a 2- to 4-fold increased risk of UGIB. Because
of this UGIB risk, aspirin is not routinely recommended for the prevention of
colorectal neoplasia.
- The use
of proton pump inhibitors (PPIs) such as omeprazole can significantly reduce
the risk of upper gastrointestinal bleeding. ACC/AHA issued a Clinical
Expert Consensus in 2008 with the following recommendation: PPIs are the preferred
agents for the therapy and prophylaxis of aspirin-associated gastrointestinal
injury.
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