Aspirin and Colorectal Cancer Risk DNA Test

Colorectal Cancer

Colorectal cancer is the third most common cancer in men and the fourth most common cancer in women in the United States. It is also one of the leading causes of deaths due to cancer in the US. Colorectal cancers include colon cancer, found in the large intestine, and rectal cancer, found in the last several inches of the colon. Several risk factors such as obesity, physical inactivity, smoking and consumption of red and processed meat have been linked to colorectal cancers.

Aspirin as a Preventative Medication

Currently many individuals at a high risk of a heart attack, or have previously suffered a heart attack, take low doses of aspirin as a preventative measure against future heart attacks. Aspirin reduces inflammation and inhibits blood clots by blocking the action of an enzyme called cyclooxygenase. Without this enzyme, the body cannot make prostaglandins, which are chemicals that control both the inflammatory response and blood clotting.

Studies have linked regular low doses of aspirin over a long period of time (more than 5 years) to reduced risk of developing colorectal cancer. This also holds true for other NSAIDs (non-steroidal anti-inflammatory drugs) such as ibuprofen. Regular use of aspirin and NSAIDs may also increase the survival rate of colorectal cancer patients.

However, aspirin has potential harmful side effects such as gastrointestinal bleeding and ulcers, ringing of the inner ear, dizziness, nausea, abdominal pain, headaches and muscle cramps. Because of these risks, a physician should be consulted before taking aspirin regularly as a preventative medication.

Genetic Variants Associated with Cancer Risk and Regular Aspirin Use

Recent studies have shown that two genetic variants may be associated with increased or decreased risk of colorectal cancer with aspirin intake: - rs2965667 on chromosome 12, near the MGST1 gene, and rs16973225 on chromosome 15, near the IL16 gene. The most common nucleotide at each marker may be associated with a decreased risk of colorectal cancer if aspirin is used regularly. At marker rs2965667, 96% of the population have the TT genotype (decreased risk), while 4% have either the TA or AA genotype (and increase their cancer risk with aspirin use). At marker rs16973225, 91% of the population have the AA genotype (decreased risk), while 9% have the AC or CC genotype (no affect on cancer risk).

Interpreting the DNA Test Results

A simple DNA test can be performed to find out which form of the two genetic markers (rs2965667 and rs16973225) are present in an individual.

Combined protective outcomes of these variants, in other words how NSAID use might affect cancer risk when both rs2965667-TT and rs16973225-AA variants are present, have not been studied.

Recommended Links:

Nan et al (2015). Association of Aspirin and NSAID Use With Risk of Colorectal Cancer According to Genetic Variants. JAMA. 313(11):1133-1142. doi:10.1001/jama.2015.1815.