Colon Cancer

Colon Cancer Overview

The human colon is a muscular, tube-shaped organ measuring about 4 feet long. It extends from the end of your small bowel to your anus, twisting and turning through your abdomen (belly). The colon has 3 main functions. 

• To digest and absorb nutrients from food
  
  
• To concentrate fecal material by absorbing fluid (and electrolytes) from it
  
  
• To store and control evacuation of fecal material

The right side of your colon plays a major role in absorbing water and electrolytes, while the left side is responsible for storage and evacuation of stool.

Cancer is the transformation of normal cells. The transformed cells grow and multiply abnormally.

• Left untreated, these cancers grow and eventually spread through the colon wall to involve the adjacent lymph nodes and organs. Ultimately, they spread to distant organs such as the liver, lungs, brain, and bones.
  
  
• Cancers are dangerous because of their unbridled growth. They overwhelm healthy cells, tissues, and organs by taking their oxygen, nutrients, and space.
  
  
• Most colon cancers are adenocarcinomas—tumors that develop from the glands lining the colon’s inner wall.
  
  
• These tumors are sometimes referred to as colorectal cancer, reflecting the fact that the rectum, the end portion of the colon, can also be affected.

In the United States, 1 in 17 people will develop colorectal cancer.

• According to reports from the National Cancer Institute, colorectal cancer is the third most common cancer in US men.
  
  
• Colorectal cancer is the second most common cancer in US women of Hispanic, American Indian/Alaska Native, or Asian/Pacific Islander ancestry, and the third most common cancer in white and African American women.
  
  
• The overall incidence of colorectal cancer increased until 1985 and then began decreasing at an average rate of 1.6% per year.
  
  
• Deaths from colorectal cancer rank third after lung and prostate cancer for men and third after lung and breast cancer for women.

Colon Cancer Causes

Most colorectal cancers arise from adenomatous polyps—clusters of abnormal cells in the glands covering the inner wall of the colon. Over time, these abnormal growths enlarge and ultimately degenerate to become adenocarcinomas.

People with any of several conditions known as adenomatous polyposis syndromes have a greater-than-normal risk of colorectal cancer.

• In these conditions, numerous adenomatous polyps develop in the colon, ultimately leading to colon cancer.
  
  
• The cancer usually occurs before age 40 years.
  
  
• Adenomatous polyposis syndromes tend to run in families. Such cases are referred to as familial adenomatous polyposis (FAP). Celecoxib (Celebrex) has been FDA approved for FAP. After 6 months, celecoxib reduced the mean number of rectal and colon polyps by 28% compared to placebo (sugar pill) 5%.

Another group of colon cancer syndromes, termed hereditary nonpolyposis colorectal cancer (HNPCC) syndromes, also run in families. In these syndromes, colon cancer develops without the precursor polyps.

• HNPCC syndromes are associated with a genetic abnormality. This abnormality has been identified, and a test is available. People at risk can be identified through genetic screening.
  
  
• Once identified as carriers of the abnormal gene, these people require counseling and regular screening to detect precancerous and cancerous tumors.
  
  
• HNPCC syndromes are sometimes linked to tumors in other parts of the body.