Colorectal cancer

Dear Alice,

What are the signs of colon cancer?

Dear Reader,

It's great that you're asking this question, as it's not always easy to figure out! Signs and symptoms of colorectal cancer may initially go unnoticed because they aren’t drastic and don’t cause pain, such as changes in bowel habits or the consistency of stool; someone may also experience persistent discomfort, gas, or cramping; a person may also have unexplained weight loss. Someone might also experience a feeling of incomplete emptying of the bowels, nausea, vomiting, and constant tiredness. Other symptoms include blood in the stool or rectal bleeding, but these could also be signs of more benign problems such as hemorrhoids or anal fissures (which are still worth talking with a health care provider about). Read on for more information about signs and symptoms, along with risk factors for colorectal cancer and how to detect it early.

Colorectal cancer, which includes cancers of both the colon (the last four to six feet of the large intestine) and the rectum, is the third most common type of cancer among individuals assigned male at birth and individuals assigned female at birth and the second leading cause of cancer-related deaths when those numbers are combined. Each year, almost 150,000 new cases are diagnosed and more than 50,000 people die from the disease. Some of the signs include various forms of gastrointestinal discomfort, but many may go unobserved since they may not be as noticeable. This is why screening is a valuable tool for early detection.

Although the specific causes of colorectal cancer is unknown, research suggests certain risk factors increase the chances of developing it, including:

  • Being over the age of 50: The majority of individuals diagnosed with colon cancer are over the age of 50, but it’s not quite clear why.
  • Personal health history: Those with inflammatory intestinal conditions (such as ulcerative colitis or Crohn's disease), inherited syndromes that can lead to colon cancer, or those with a family history of colon cancer are at an increased risk.
  • Increased consumption of red or processed meat: The International Agency for Research on Cancer considers processed meats to be carcinogenic and red meats to be probably carcinogenic.
  • Following a low-fiber, high fat diet: The research has been mixed, but there seems to be an association between colon cancer diagnosis and patterns of eating that are low in fiber, such as fruits and vegetables, and high in fat.
  • Alcohol consumption and cigarette smoking: These behaviors have been correlated to an increase risk of colon cancer.
  • Obesity: Individuals who are have higher body fat percentages may be at an increased risk of dying from colon cancer compared to those with average amounts of body fat.
  • Lack of physical activity: Those who lead a more sedentary lifestyle are at increased risk of colon cancer; in fact, some studies show that physical activity may reduce the risk.

List adapted from Mayo Clinic.

Since the causes aren’t completely clear and symptoms may not be as obvious early on, it’s wise to get screened regularly, particularly for people over the age of 50 and those with risk factors. Screening typically includes testing for blood in the stool and a sigmoidoscopy. This procedure is conducted by inserting a small flexible scope into the rectum to view the lower part of the colon for abnormal growths, called polyps, which can develop into cancer over time. If polyps are detected during a screening, they can be removed before they become cancerous or have a chance to spread. A health care provider can help determine the specific screening method and frequency based upon the individual’s medical and family history. Getting screened is the best prevention because when detected early, colon cancer has a 90 percent survival rate.

For more information about colorectal cancer, check out the, Centers for Disease Control and Prevention, the National Cancer Institute, and the American Cancer Society.

Last updated Jul 31, 2020
Originally published Jun 13, 2003

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