Colorectal cancer screening: Guidelines, options and risks


COLORECTAL cancer is the third most commonly diagnosed cancer in the United States, but with timely screenings, it is also one of the most preventable, according to the American Cancer Society (ACS). A colorectal-cancer screening can usually detect precancerous polyps, and these growths can then be removed during a colonoscopy long before they become malignant.
“This is a cancer people don’t need to die from,” said Dr. Andrew Wolf, an oncologist and an associate professor of medicine at the University of Virginia School of Medicine. “It’s a very screenable disease.”
The two main types of colorectal-cancer screenings are a colonoscopy and a stool-based test. A colonoscopy uses imaging technology to provide pictures of the colon’s inner wall. With a stool test, lab technicians examine a stool sample for signs of disease.
Cancer is an abnormal growth of cells that invade healthy tissue. Cancer cells can form tumors in the areas where they originate, and they can spread to other parts of the body and grow there, according to the ACS. Colorectal cancer usually begins as a polyp in the wall of the colon or the rectum. Depending on where the cancer starts, it may be called colon cancer or rectal cancer.
Polyps can be bulb-shaped or flat. Not all polyps become cancerous, but certain types are more likely to turn into cancer. There are two main types of colorectal polyps, according to the ACS:
Hyperplastic polyps and inflammatory polyps, which are more common but usually are not precancerous. Adenomatous polyps (adenomas), which form less often but, because they occasionally change into cancer, are considered precancerous.
There is no specific cause of colorectal cancer, but there are risk factors for developing the disease. One of the main risk factors is genetics; people with a family history of colorectal cancer are more likely to have polyp formation and cancer than individuals with no family history of the condition, according to the Mayo Clinic. Two genetic disorders are also associated with a higher risk of developing colorectal cancer: familial adenomatous polyposis and Lynch syndrome.
Diet and lifestyle may also play roles. Western diets that contain too much red meat and saturated fat may boost the risk of colorectal cancer, said Dr. Mark Friedman, a gastroenterologist with Moffitt Cancer Center in Tampa, Florida. In countries such as Japan, where the standard diet doesn’t include as much red meat, the risk of colon cancer is lower, according to the World Cancer Research Fund International.
The risk of developing colorectal cancer for people ages 45 to 49 is about the same as for people ages 50 to 54, according to research by the American Cancer Society, which used to recommend screenings start at age 50.
“Poor diet and dramatic increases in obesity and type 2 diabetes rates may be partly responsible for the rise in younger colorectal cancer cases, but there may be other factors,” Friedman told Live Science.

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