Colorectal Cancer

Colorectal cancer is unregulated cell growth in the colon or rectum. Cancers of the colon and rectum are classified together because they are genetically identical; though, this form of cancer may be referred to as colon cancer or rectal cancer depending on where it starts. The colon (large intestine or large bowel) is a muscular tube that joins the small intestine right below the right lower abdomen and the rectum. The purpose of the colon is to absorb water and salt from food and process waste matter. Cancer that forms in the colon interferes with these normal processes. The rectum is the end part of the digestive tract; it acts as temporary storage for stool before it passes outside the body. Among other things, cancer of the rectum may interfere with normal defecation habits. Colorectal cancer is the third most frequently occurring cancer1.

Credit: American Cancer Society

What different types of colorectal cancer exist?

There are several types of colorectal cancer that affect the different cells of this portion of the intestinal tract. Read more about the types of colorectal cancer at: 

What are the symptoms of colorectal cancer?

Colorectal cancer often develops without symptoms. By the time symptoms are noticeable, the cancer is likely in an advanced stage. When symptoms do occur, they may include:

  • Rectal bleeding or blood in the stool
  • Weakness
  • Changes in bowel movements (such as diarrhea, constipation or narrowing of the stool)
  • Weight loss
  • Nausea and/or fatigue
  • Discomfort or the urge to have a bowel movement when there is no need to go
  • Abdominal pain and/or cramping

How is colorectal cancer diagnosed?

Physical exams for colorectal cancer will include a digital rectal exam in which a gloved finger is inserted into the rectum to feel for abnormalities.

Fecal tests check for the presence of blood in the stool, a possible indicator of colorectal cancer. These tests include the occult blood test, a take-home test that measures the actual amount of blood in stool. The fecal immunochemical test is another take-home test that finds blood proteins, also known as “hidden blood,” in the stool.

Endoscopic tests are the examination of the colon and rectum using instruments that are inserted into the anus. Endoscopic instruments typically have lights on the probing end, which allows the doctor to check for abnormalities in the colon or rectum. Specific endoscopic tests for colorectal cancer include: sigmoidoscopy and endoscopic ultrasounds.

Imaging tests use x-rays, magnets, sound waves or radioactive substances to create pictures of the inside of the body. For colorectal cancer, these tests may include intravenous pyelograms, computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, positron emission tomography (PET) scans, ultrasounds, chest x-rays and angiography, all of which are particularly good at detecting if colorectal cancer has spread to other organs.

Biopsies are the removal of a small piece of colorectal tissue that is microscopically examined for the presence of colorectal cancer.

Blood tests help determine the presence of colorectal cancer and monitor its progress. These tests include a complete blood count, liver enzyme tests and tumor marker tests.

What are the different stages of colorectal cancer?

The most commonly used staging system for colorectal cancer is that of the American Joint Committee on Cancer (AJCC), sometimes also known as the TNM system.

The TNM system describes 3 key pieces of information:

  • T describes how far the main (primary) tumor has grown into the wall of the intestine and whether it has grown into nearby areas.
  • N describes the extent of spread to nearby (regional) lymph nodes. Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections.
  • M indicates whether the cancer has spread (metastasized) to other organs of the body. (Colorectal cancer can spread almost anywhere in the body, but the most common sites of spread are the liver and lungs.

What are the treatments for colorectal cancer?

This colorectal cancer treatment information does not outline the particular treatment(s) a patient will receive. Rather, it provides general information about the typical therapies used for this type of cancer.

Primary treatment options:

  • Surgery is the physical removal of colorectal tumors, surrounding tissues and, if needed, nearby lymph nodes to prevent the cancer from recurring. It is often the main treatment for earlier stage colon cancers, and it is the main treatment for rectal cancers with radiation and chemotherapy often delivered before and/or after surgery.
  • Chemotherapy is the use of drugs to treat cancer. It is most often used as treatment for stage 3 colon cancer and colon cancer that has spread to secondary locations. For rectal cancer, chemotherapy is often delivered before surgery to shrink a tumor to operable size and after surgery to help prevent recurrence.
  • Radiation Therapy uses high-energy rays or particles to kill cancer cells. Radiation therapy is used to treat colon cancer that cannot be completely removed during surgery due to spreading of the cancer. For rectal cancer, radiation therapy is given before surgery and after to prevent recurrence.

Secondary treatment options:

  • Targeted Therapies are drugs designed to target the underlying gene and protein changes to colorectal cancer cells and prevent the mutations that cause tumors. They can be used either along with chemotherapy or by themselves if chemotherapy is no longer working.

What are the risk factors of colorectal cancer?

  • Age: People over the age of 50 are at higher risk of developing colorectal cancer.
  • Race/ethnicity: African Americans have the highest incidence of colorectal cancer in the United States.
  • Body fat: Obesity increases the risk of developing colorectal cancer.
  • Genetics: About 20% of colorectal cancers are linked to gene mutations.
  • Family history: Those with a family history of colorectal cancer before age 55, especially in a parent or sibling, are at high risk for colon cancer.
  • Diet/exercise: A lack of exercise and high intake of red and processed meats can increase a person’s risk of developing colon cancer.
  • Alcohol/smoking: The use of alcohol and smoking tobacco is linked to higher rates of colorectal cancer.
  • History of inflammatory bowel disease (IBD): Having IBD, ulcerative colitis and/or Crohn’s disease increases the risk of developing colorectal cancer.
  • Type II diabetes: Studies have determined colorectal cancer is linked to type II diabetes.

How can I prevent getting colorectal cancer?

  • Having regular exams of the colon and rectum is the best way to reduce the risk of developing colorectal cancer.
  • Eating a low-fat, high-fiber diet that includes at least five servings of fruits and vegetables each day is correlated to lower rates of colorectal cancer. 
Mikayla D. Williams , BS student, Nursing , The University of Arizona
Michael Principe, MA, Information Resources and Library Science , The University of Arizona
Works Cited: 
Center for Disease Control (2013). In Cancer and Men.
American Cancer Society (2014). Colon/Rectum Cancer.
Works Consulted: 
Colon Cancer Alliance (2014). Prevention & Screening.
Preventing Colorectal Cancer (2014). In Colorectal Cancer Health Center.
Memorial Sloan Kettering Center (2014). About Colorectal Cancer. In Colorectal Cancer.
Cancer Treatment Centers of America (2014). Colorectal Cancer. In About Your Cancer.