Colorectal cancer is preventable and highly curable if detected in early stages. The colon is the first 4 to 5 feet of the large intestine. The rectum is the last portion of the colon. Colorectal cancer tumors grow in the colon’s inner lining.



In 2017, nearly 136,000 new cases of colorectal cancer were expected to be diagnosed in the U.S. About 1 in 20 (5%) Americans will develop colorectal cancer during their lifetime.

Colorectal polyps (benign abnormal growths) affect about 20% to 30% of American adults.



The exact cause of colorectal cancer is unknown. Physicians often cannot explain why one person develops this disease and another does not. However, the understanding of certain genetic causes continues to increase. The following factors can increase one’s risk of colorectal cancer.

  • Age: More than 90% of people are diagnosed with colorectal cancer after age 50.
  • Family history of colorectal cancer (especially parents or siblings).
  • Personal history of Crohn’s disease or ulcerative colitis for eight years or longer.
  • Colorectal polyps.
  • Personal history of breast, uterine or ovarian cancer.



Colorectal cancer is preventable. Nearly all cases of colorectal cancer develop from polyps. They start in the inner lining of the colon and most often affect the left side of the colon. Detection and removal of polyps through colonoscopy reduces the risk of colorectal cancer. Colorectal cancer screening recommendations are based on medical and family history. Screening typically starts at age 50 in patients with average risk. Those at higher risk are usually advised to receive their first screening at a younger age.

While it is not definitive, there is some evidence that diet may play a significant role in preventing colorectal cancer. A diet high in fiber (whole grains, fruits, vegetables and nuts) and low in fat is the only dietary measure that may help prevent colorectal cancer.



Colorectal cancer often causes no symptoms and is detected during routine screenings. It is important to note that other common health problems can cause some of the same symptoms. For example, hemorrhoids are a common cause of rectal bleeding, but do not cause colorectal cancer.

Colorectal cancer symptoms include:

  • A change in bowel habits (e.g. constipation or diarrhea).
  • Narrow shaped stools.
  • Bright red or very dark blood in the stool.
  • Ongoing pelvic or lower abdominal pain (e.g., gas, bloating or pain).
  • Unexplained weight loss.
  • Nausea or vomiting.
  • Feeling tired all the time.

Abdominal pain and weight loss are typically late symptoms, indicating possible extensive disease. Anyone who experiences any of the above symptoms should see a physician as soon as possible.



  • Physical exam and medical history.
  • Blood tests.
  • Colonoscopy: Examination of the entire colon with a long, thin flexible tube with a camera and a light on the end (colonoscope).
  • Biopsy: Removal of cells or tissues so they can be viewed under a microscope to check for signs of cancer.


The following tests may be used for staging:

  • Computed Tomography (CT) scan: A highly sensitive x-ray test that allows physicians to see “inside” the body to identify new or recurrent tumors. This test can accurately detect the presence of most cancer cells that have spread outside of the colon.
  • Positron emission tomography (PET) scan: An imaging test that uses a special dye that has radioactive tracers. This allows physicians to detect the presence of most cancer cells that have spread outside of the colon.
  • CEA assay: Carcinoembryonic antigen is a substance in the blood that may be elevated if cancer is present. Although not completely conclusive on its own, this test is often done with other diagnostic tests.
  • Magnetic Resonance imaging (MRI): An imaging test that uses a magnetic field and pulses of radio wave energy to create pictures of organs and structures inside the body. This helps determine if the tumor has spread through the wall of the rectum and invaded nearby structures.
  • Abdominal ultrasound: A procedure in which a transducer is moved along the skin over the abdomen. This test looks for tumors that may have spread to the liver, gallbladder, pancreas or elsewhere in the abdomen.


The extent of cancer (clinical stage) is linked to treatment decision making and post-treatment patient outcome. Staging is based on whether the tumor has invaded nearby tissues or lymph nodes, and/or cancer has spread to other parts of the body. The exact stage is often not determined until after surgery.



American Society of Colorectal Surgeons