Colorectal Cancer Overview

Colon and rectal cancer are cancers that involve the lowest part of the digestive system (the colon is the same as the large intestine). Colorectal cancer is the second leading cause of cancer deaths in the United States, accounting for 14 percent of cancer deaths. Colorectal cancer is usually preventable if precancerous polyps are detected and removed before they become malignant (cancerous). Polyps develop from a genetic mutation in the colon cells. Over time, small polyps can develop additional mutations and become cancerous. Polyps are usually removed when they are found on colonoscopy. Colon cancer can be prevented in many cases by undergoing screening colonoscopy to find and remove polyps before they turn malignant.


In the earlier (and sometimes even in later) stages colon cancer can cause NO symptoms.  This is why screening for colon polyps and cancer is so important. When symptoms occur, they most commonly are: abdominal pain, bloody bowel movements, changes in usual bowel habit (development of constipation, diarrhea, or both), fatigue, and weight loss.


The diagnosis of colorectal cancer is usually made during colonoscopy. At that time, a biopsy (removal of a piece of tissue for examination) can be done, confirming the presence of a cancer. A CT scan can assess the tumor and look for metastasis (spread of tumor).

Endoscopic ultrasound involved inserting a special scope that has an ultrasound probe on it into the rectum. In rectal cancer, this can accurately assess the size of the tumor and look for local spread outside the wall of the rectum and lymph nodes.


Staging is a system used to describe the location(s) and aggressiveness and spread of a cancer. Early on, the cancer is confined to the colon. With time it can spread to surrounding tissues, to lymph nodes, and to reomote areas such as the liver and elsewhere.

Colorectal cancer stages range from stage I (cancer has invaded into but not through the entire wall of the intestine), to stage IV (the cancer has spread to distant organs, such as the liver). Treatment depends on disease stage.

Earlier stages of disease (stages I through III) are referred to as localized colorectal cancers and generally treated with surgery, with or without chemotherapy. When the cancer is in the rectum, radiation therapy may be used.

Stage IV cancer is called advanced colorectal cancer and is generally treated with chemotherapy; some patients may benefit from surgery.


The treatment of colon cancer depends on the stage determined at diagnosis or after surgery. Localized cancer is usually treated surgically. If lymph nodes are involved, chemotherapy is added. If the cancer has metastasized (spread) to other areas, surgery may be used for the main cancer and chemotherapy may address the tumor outside the colon.


The majority of rectal cancers are treated with a combination of surgery, radiation therapy, and chemotherapy; as with colon cancers, treatment is chosen based upon disease stage. Stage I rectal cancer may be treated with surgery alone. Stage II and III is usually treated with chemotherapy, radiation therapy, and surgery. Stage IV cancer is predominantly treated with chemotherapy, with or without surgery.

Neoadjuvant chemoradiotherapy involves a combination of chemotherapy and radiation therapy before surgery. This treatment aimes to shrink the tumor before it is removed, reduces the risk that the cancer will come back.


First-degree relatives (a parent, brother, sister, or child) of a person who has been diagnosed with an adenomatous polyp (or colorectal cancer) before the age of 60 years have an increased risk of developing adenomatous polyps and colorectal cancer compared to the general population. Thus, family should be made aware if the person is diagnosed with an adenoma or colon cancer.

While screening for polyps and cancer is recommended for everyone (typically beginning at age 50), those at increased risk should begin screening earlier, typically at age 40. Colonoscopy is the recommended test for colon cancer screening.

Certain genetic conditions increase the risk of colon cancer. The most common conditions include Lynch syndrome or hereditary nonpolyposis colon cancer (HNPCC), and familial adenomatous polyposis (FAP).  A strong family history of colon cancer (two or more close relatives) should be discussed in detail. Genetic testing can more fully evaluate an individual’s and family risk of colon and other cancers.

Relatives can be told the following:

  • People who have one first-degree relative (parent, brother, sister, or child) with colorectal cancer or an adenomatous polyps at a young age (before the age of 60 years), or two first-degree relatives diagnosed at any age, should begin screening for colon cancer earlier, typically at age 40, or 10 years younger than the earliest diagnosis in their family, whichever comes first. Screening usually includes colonoscopy, which should be repeated every five years.
  • People who have one first-degree relative (parent, brother, sister, or child) with colorectal cancer or an adenomatous polyp at age 60 or later should begin screening at age 40. If the examination shows no polyps, it should be repeated similar to a person with an average risk of colon cancer.
  • People with a second-degree relative (grandparent, aunt, or uncle) or third-degree relative (great-grandparent or cousin) with colorectal cancer should be screened for colon cancer similar to a person with an average risk
  • Some conditions, such as hereditary nonpolyposis colorectal cancer (Lynch syndrome), familial adenomatous polyposis, MUTYH- associated polyposis, and inflammatory bowel disease (eg, ulcerative colitis, Crohn’s disease) significantly increase the risk of colon polyps or cancer in family members. Colon cancer screening in this group is discussed individually.