Colorectal Polyps/Cancer and the Benefits of Aspirin Therapy
Colorectal cancer, often referred to as colon cancer, is cancer that develops in the colon or rectum. Most people know the colon as thelarge intestine or the large bowel. The majority of colorectal cancers start as colorectal polyps, growths inside the colon or rectum that may later become cancerous.
Excluding skin cancers, colorectal cancer is the third most common type of cancer diagnosed in men and women in the United States today. The disease affects both men and women equally and risk increases as a person ages. According to the American Cancer Society, the risk of a person developing colorectal cancer during their lifetime is about 1 in 19. Colorectal cancer is currently the second leading cause of cancer death in the United States. In 2008, there were approximately 150,000 new cases and 50,000 colorectal cancer-related deaths in the United States.
Preventative screening measures can help detect many colorectal cancers early, when they are more treatable. Colonoscopy is considered to be the gold standard in colorectal cancer screening. An estimated 14 million colonoscopies are performed 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 Polyps and Cancer
Over the past 30 years, a number of controlled research studies have suggested that aspirin therapy can inhibit carcinogenesis, in the large bowel. Aspirin works by blocking an enzyme known as Cox-2, 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 have been found to over-express this enzyme.
In 2008, the 5th International Conference on Cancer Prevention produced an international consensus statement that “evidence clearly shows a chemopreventive effect for aspirin.”
Recently, two other groundbreaking studies, the Nurses’ Health Study and the Health Professionals Follow-up Study, also concluded that the regular use of aspirin after the diagnosis of colorectal cancer is associated with a significant reduction in a person’s risk of dying from the disease.
Aspirin and the Risk of Upper Gastrointestinal Bleeding
Although the benefits of aspirin in colorectal neoplasia (adenomatous polyps and cancer) reduction 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. The American College of Cardiology and the American Heart Association issued a Clinical Expert Consensus in 2008 recommending PPIs as the preferred agents for the therapy and prophylaxis of aspirin-associated gastrointestinal injury.