Colorectal cancer is one of the most commonly diagnosed cancers in the world, with about 140,000 total cases presented in 2019 in the United States alone. It generally affects older adults and begins as abnormal cell growths called “polyps” form on the inner lining of the colon (also known as the large intestine) or the rectum. Adenomatous polyps (adenomas) are referred to as “precancerous” conditions because they often develop into cancer, while hyperplastic polyps and inflammatory polyps—though generally more common— do not tend to develop into cancer.
The stage (extent of spread) of the disease is determined by the magnitude and location of the polyp growth. The colon and rectum are comprised of many layers (from the innermost mucosa layer to the outermost adventitia layer), and once the cancer cells are attached to the innermost layer, they spread out and into lymph and blood vessels. From there, they can travel to other more remote parts of the body.
- A change in frequency of bowel movements: Prolonged constipation or diarrhea (longer than a week) can indicate the formation of a polyp.
- Abdominal pain or cramps: Because a large polyp can obstruct your bowel, it can cause pain in the abdominal region.
- Anemia: Polyps bleed, and when they do so chronically, can deplete your body of the iron it requires to produce hemoglobin (the protein used to carry oxygen to blood).
- Blood in stool: Particularly if it’s bright red and accompanied by abdominal pain, it can be a result of bleeding polyps.
- Nausea and vomiting: When accompanied by abdominal pain, it can indicate a gastrointestinal issue.
- Unexplained weight loss: This usually occurs in advanced stages as a result of diarrhea, vomiting, and pain, all of which may eating difficult.
Who is at risk?
Because colorectal cancer generally affects older adults, this is the population most at risk of developing it. However, measures of daily lifestyle practices such as diet, exercise, and smoking also have a dramatic impact on the probability of diagnosis. Finally, colon cancer can be genetic; a family history of colon and affiliated cancers (including Lynch syndrome and adenomatous polyposis) put patients at a higher risk of developing colorectal cancer.
When to see a doctor
The Memorial Sloan Kettering Cancer Center recommends that if you have an average risk of development and no symptoms, you get screened once every 10 years beginning at age 50. However, if you are at a higher risk or are experiencing one or more of the aforementioned symptoms, you should have screenings more frequently.