You are here

Colon Cancer

Colon Cancer | ASCRS

Colon cancer (commonly referred to as 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. 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 45* 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.

*In 2018, secondary to new data on the increased risks of colon cancer in those under 50, the American Society of Colon and Rectal Surgery changed recommendations to consider starting screening at age 45. 


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 imagin (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. 


Surgery to remove the colorectal cancer is almost always required for a complete cure. The tumor and lymph nodes are removed, along with a small portion of normal colon on either side of the tumor. A colostomy is a surgically created opening that connects a part of the colon to the skin of the abdominal wall. This procedure is typically only done in a very small number of colorectal cancer patients.

Minimally invasive surgical techniques may be used by trained surgeons based on the individual case. Your surgeon will discuss this with you prior to surgery and decide on the most optimal approach. 


Chemotherapy may be offered either before or after surgery, depending on the stage of the cancer. Unlike rectal cancer, radiation therapy is rarely used for colorectal cancer. 


Patient outcome is strongly associated with colorectal cancer stage at the time of diagnosis. Cancer confined to the lining of the colon is associated with the highest likelihood of success. This is one reason why early detection through screening methods like colonoscopy is crucial.

Follow-up care after treatment for colorectal cancer is important. Even when the cancer appears to have been completely removed or destroyed, the disease may recur. Undetected cancer cells can remain in the body after treatment. Your colon and rectal surgeon will monitor your recovery and check for cancer recurrence at specific intervals. Blood tests, clinical examinations and imaging tests may be performed based on the stage of the cancer.


Colon and rectal surgeons are experts in the surgical and non-surgical treatment of diseases of the colon, rectum and anus. They have completed advanced surgical training in the treatment of these diseases as well as full general surgical training. Board certified colon and rectal surgeons complete residencies in general surgery and colon and rectal surgery, and pass intensive examinations conducted by the American Board of Surgery and the American Board of Colon and Rectal Surgery. They are well-versed in the treatment of both benign and malignant diseases of the colon, rectum and anus and are able to perform routine screening examinations and surgically treat conditions if indicated to do so.



The American Society of Colon and Rectal Surgeons is dedicated to ensuring high-quality patient care by advancing the science, prevention and management of disorders and diseases of the colon, rectum and anus. These brochures are inclusive but not prescriptive. Their purpose is to provide information on diseases and processes, rather than dictate a specific form of treatment. They are intended for the use of all practitioners, health care workers and patients who desire information about the management of the conditions addressed. It should be recognized that these brochures should not be deemed inclusive of all proper methods of care or exclusive of methods of care reasonably directed to obtain the same results. The ultimate judgment regarding the propriety of any specific procedure must be made by the physician in light of all the circumstances presented by the individual patient.