What is colon cancer?

The colon and the rectum together make up the large intestine, which is part of the digestive system. Malignant tumors can be found in either the colon or rectum.  The colon or large bowel includes the first six feet of the large intestine, and the rectum and the anal canal includes the last six inches. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body.

What are the symptoms of colon cancer?

The following are the most common symptoms of colorectal cancer. However, each individual may experience symptoms differently.   People who have any of the following symptoms should check with their physicians, especially if they are over 50 years old or have a personal or family history of the disease:

• a change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
• rectal bleeding or blood in the stool
• cramping or gnawing stomach pain
• decreased appetite
• vomiting
• weakness and fatigue
• jaundice (yellowish coloring) of the skin or sclera of the eye

The symptoms of colorectal cancer may resemble other conditions, such as infections, hemorrhoids, and inflammatory bowel disease. It is also possible to have colon cancer and not have any symptoms. Always consult your physician for a diagnosis.

What causes colon cancer?

The exact cause of colorectal cancer is unknown. Age and health history can affect the risk of developing colorectal cancer. Approximately 25 percent of individuals with colorectal cancer have at least one relative with colorectal cancer, while 75 percent of cases are persons without a family history. 

Approximately 5 to 6 percent of colorectal cancers are due to known predisposing genetic factors. This means that the majority of colorectal cancers are, in fact, not inherited. Specifically, 3 percent to 5 percent of all colorectal cancer is due to hereditary nonpolyposis colon cancer (HNPCC), while approximately 1 percent is due to familial adenomatous polyposis (FAP).

Who gets colon cancer?

The following are some of the risk factors for colon cancer:

• Age: Most people who have colorectal cancer are over age 50, however, it can occur at any age.
• Polyps: Benign growths on the wall of the colon or rectum are common in people over age 50, and are believed to lead to colorectal cancer.
• Personal history: People who have had colorectal cancer, as well as ovarian, uterine, or breast cancers, have a slightly increased risk for colorectal cancer.
• Family history: People with a strong family history of colorectal cancer or  polyps in a first-degree relative (in a parent or sibling before the age of 60 or in two first-degree relatives of any age), have an increased risk for colorectal cancer.
• Ulcerative colitis: People who have ulcerative colitis, an inflamed lining of the colon, have an increased risk for colorectal cancer.
• Obesity
• Physical inactivity
• High-fat and/or low-fiber diet
• Alcohol consumption
• Diabetes

How is colon cancer related to Crohn’s and Ulcerative Colitis?

Individuals with ulcerative colitis have a higher risk of developing colon cancer due to the inflamed lining of their colon. Colorectal cancers may develop more rapidly in patients with Crohn’s and ulcerative colitis. Colorectal cancers also may begin as microscopic changes in the lining of the colon (called dysplasia) that may not be visible unless multiple biopsies are taken of the colon during a colonoscopy.

In general, if a person has had Crohn’s or ulcerative colitis for more than 8 years or they are over the age of 50, they will need a colonoscopy to look for colon cancer. Recommendations for different patients may vary depending on the IBD type, duration and the length of involvement of the colon.

Different than a regular colonoscopy, for patients with Crohn’s or ulcerative colitis, the doctor performing the colonoscopy has to take multiple biopsies of the colon (typically more than 30 to 40) even if the colon lining looks completely normal to detect early microscopic changes related to colorectal cancer.

How is colon cancer diagnosed?

• Digital rectal examination (DRE) - a physician or healthcare provider inserts a gloved and lubricated finger into the rectum to feel for anything unusual or abnormal. This test can detect cancers of the rectum, but not the colon.
• Fecal occult blood test - checks for hidden (occult) blood in the stool. It involves placing a very small amount of stool on a special card, which is then tested in the physician’s office or sent to a laboratory. This test is not needed if the patient is having either colonoscopy or a barium enema.

• One of the following:
  • Flexible sigmoidoscopy - a diagnostic procedure that allows the physician to examine the inside of a portion of the large intestine, and is helpful in identifying the causes of diarrhea, abdominal pain, constipation, abnormal growths, and bleeding. A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum. The scope blows air into the intestine to inflate it and make viewing the inside easier.
  • Colonoscopy - a procedure that allows the physician to view the entire length of the large intestine, and can often help identify abnormal growths, inflamed tissue, ulcers, and bleeding. It involves inserting a colonoscope, a long, flexible, lighted tube, in through the rectum up into the colon. The colonoscope allows the physician to see the lining of the entire colon, remove tissue for further examination, and possibly treat some problems that are discovered. 
  • Barium enema with air contrast (Also called a double contrast barium enema.) - a fluid called barium (a metallic, chemical, chalky, liquid used to coat the inside of organs so that they will show up on an x-ray) is given into the rectum to partially fill up the colon. An x-ray of the abdomen shows strictures (narrowed areas), obstructions (blockages), and other problems.

How is colon cancer treated?

Specific treatment for colorectal cancer will be determined by your physician based on:

• your age, overall health, and medical history 
• extent of the disease 
• your tolerance for specific medications, procedures, or therapies 
• expectations for the course of this disease 
• your opinion or preference

After the colorectal cancer is diagnosed and staged, your physician will recommend a treatment plan. Treatment may include: 

• Colon surgery: Often, the primary treatment for colorectal cancer is an operation called a colon resection, in which the cancer and a length of normal tissue on either side of the cancer are removed, as well as the nearby lymph nodes.
• Radiation therapy: Radiation therapy is the use of high-energy radiation to kill cancer cells and to shrink tumors. There are two ways to deliver radiation therapy, including the following:
  • external radiation (external beam therapy) - a treatment that precisely sends high levels of radiation directly to the cancer cells. The machine is controlled by the radiation therapist. Since radiation is used to kill cancer cells and to shrink tumors, special shields may be used to protect the tissue surrounding the treatment area. Radiation treatments are painless and usually last a few minutes.
  • internal radiation (brachytherapy, implant radiation) - radiation is given inside the body as close to the cancer as possible. Substances that produce radiation, called radioisotopes, may be swallowed, injected, or implanted directly into the tumor. Some of the radioactive implants are called “seeds” or “capsules.”

• Chemotherapy
  Chemotherapy is the use of anticancer drugs to treat cancerous cells. In most cases, chemotherapy works by interfering with the cancer cell’s ability to grow or reproduce. Different groups of drugs work in different ways to fight cancer cells. The oncologist will recommend a treatment plan for each individual. Studies have shown that chemotherapy after surgery can increase the survival rate for patients with some stages of colon cancer. Chemotherapy can also help relieve symptoms of advanced cancer.