Colorectal Cancer

Colon cancer and rectal cancer start the same way and share many risk factors and symptoms. The two are often referred to together as colorectal cancer. There are some significant differences between them, though.

Colon cancer that has not spread to distant parts of the body is usually treated with surgery, if feasible. If surgery is performed, doctors determine whether the patient needs additional treatments like chemotherapy.

Rectal cancer that has not spread to distant parts of the body is also treated with surgery. For some patients, radiation therapy and chemotherapy are used to decrease the risk of the cancer returning after treatment. In some cases, radiation therapy and chemotherapy can reduce the need for surgery. Rectal cancer surgery can be more complex than colon cancer surgery.

How does colorectal cancer start?

Colorectal cancer usually starts as a polyp. Polyps are small overgrowths in the tissue lining the colon or rectum. Polyps are not cancer.

Some polyps can turn into cancer over time. Most of these polyps are adenomas, which begin in mucus-producing gland cells that line the intestine and other organs. Adenomas are considered pre-cancerous growths.

It can take several years for an adenoma to develop into cancer. When it does, the cancer is called adenocarcinoma. This is the most common type of colorectal cancer.

There are other, rarer types of colorectal cancer, including colorectal neuroendocrine tumors and rectal cancers that involve the cells of the anus.

There are more than 150,000 colorectal cancer diagnoses in the U.S. each year. As of 2018, the disease’s five-year survival rate is about 65%. This figure does not include people diagnosed more recently, who could benefit from new treatments.

Colorectal cancer symptoms

Colorectal cancer usually starts in small polyps (overgrowth of tissue) in the colon or rectum. These polyps may not produce any symptoms, especially in the early stages. As the disease progresses, more symptoms may appear. 

Symptoms of colorectal cancer may include:

• Diarrhea or constipation that does not go away
• Change in normal bowel habits, such as size, shape and frequency
• Discomfort or the urge to have a bowel movement when there is no need
• Discomfort or pain during bowel movements
• Discomfort when sitting
• Abdominal pain or cramping pain in your lower stomach
• Bloating or full feeling
• Change in appetite
• Rectal bleeding
• Blood in the stool or toilet after a bowel movement
• Excessive fatigue
• Weight loss without dieting

In the later stages of colorectal cancer, the polyp may metastasize (spread) to other parts of the body. This can cause other symptoms, depending on where cancer has spread.

These symptoms usually do not mean you have colorectal cancer. However, any time you notice unexplained changes and they persist for more than two weeks, don’t assume they will just go away. See your doctor.

Young-onset colorectal cancer

Historically, most cases of colorectal cancer have been in people over age 55. In recent years, there has been an increase in diagnoses among people under age 55. MD Anderson’s Young-onset Colorectal Cancer Program offers specialized services for these patients. Services include fertility care, genetic testing and counseling, as well as support groups for young adults.

Colorectal cancer screening

Most precancerous polyps produce few, if any, symptoms. It is important to get screened regularly for colorectal cancer. Colorectal cancer screenings allow doctors to find and remove polyps before they turn into cancer. Screening can prevent most cases of colorectal cancer. It can also catch colorectal cancer early, when treatments are more likely to be successful.

• Learn more about colorectal cancer screenings

Colorectal cancer risk factors

Anything that increases your chance of getting colorectal cancer is a risk factor. Colorectal cancer risk factors include:

• Age: More than 75% of colorectal cancer cases are diagnosed in patients age 55 and older. The median age at diagnosis is 66 years old. However, the rate of colorectal cancer diagnosed in adults less than 55 years old has increased in recent years.
• Race: African Americans have the highest rate of colorectal cancer among all racial groups in the United States.
• Family history: People whose relatives have had colorectal cancer or colorectal polyps have an increased risk of colorectal cancer.
• Inflammatory bowel disease: Patients with conditions that include Crohn’s disease or chronic ulcerative colitis are more likely to develop colon cancer. Learn more about inflammatory bowel disease and colorectal cancer.
• Personal history of colorectal cancer or polyps: People who have previously had colorectal cancer or colon polyps are at an increased risk of developing colorectal cancer.
• Hereditary cancer syndromes: Some genetic changes can be inherited and increase your risk for certain types of cancer. Inherited syndromes including hereditary nonpolyposis colorectal cancer, or Lynch syndrome, and familial adenomatous polyposis may put you at higher risk for developing colorectal cancer. Learn more about hereditary cancer syndromes.
• Diet: A diet heavy in red meat, processed meats, or meats cooked at very high heat can increase a person’s colon cancer risk.
• Obesity: Obesity increases a person’s chance of developing many different diseases, including colorectal cancer.
• Sedentary lifestyle: A lack of movement and exercise is a risk factor for colorectal cancer.
• Tobacco: Tobacco use, including cigarettes and chewing tobacco, is a colorectal cancer risk factor.
• Drinking too much alcohol: Heavy drinkers are at an increased risk for colorectal cancer.

For patients concerned about inherited family syndromes that cause colorectal cancer, we offer advanced genetic testing and counseling to help understand your risk.

Colorectal cancer prevention

Lifestyle choices that may decrease your risk of getting colorectal cancer include:

• Regular screening tests
• Staying at a healthy weight
• Regular exercise
• Eating a healthy diet with lots of fruits and vegetables
• Avoiding cigarette smoking
• Drinking alcohol only in moderation