Colorectal cancer is a disease in which cancer cells grow in the colon and/or rectum. The colon and the rectum are parts of the large intestine, which is part of the digestive system.

Cancer occurs when cells in the body (in this case colon or rectum cells) divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissue and can spread to other parts of the body. A benign tumor does not invade or spread.

Causes

The cause of colorectal cancer is unknown. However, research shows that certain risk factors are associated with the disease.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

• Age: 50 or older

• Diets high in fat and low in fiber

• Polyps (benign growths) in the colon and rectum (especially due to familial polyposis, an inherited condition)

• Personal history of colorectal cancer

• Family history of colorectal cancer, especially a parent, sibling, or child

• Ulcerative colitis (inflammation of the lining of the colon) or Crohn’s disease

• Other risk factors include: obesity, physical inactivity, diabetes, smoking, alcohol intake, nightshift work, and ethnic background

Symptoms

Colorectal cancer often does not have any symptoms, but some symptoms associated with colorectal cancer include:

• A change in bowel habits such as diarrhea, constipation, or feeling that the bowel does not empty completely, lasting for more than a few days in people over age 50

• Blood (either bright red or very dark) in the stool

• Stools that are narrower than usual

• Abdominal discomfort (frequent gas pains, bloating, fullness, and/or cramps)

• Unexplained weight loss

• Constant fatigue

Note: These symptoms may also be caused by other, less serious health conditions. Anyone experiencing these symptoms should see a doctor.

Diagnosis

The doctor will ask about your symptoms and medical history and perform a physical exam.

Tests include:

Digital Rectal Exam – use of a physician's gloved finger to examine the rectum for lumps or growths

Fecal Occult Blood Test – a test to check for hidden blood in the stool

X-rays (using barium, called a barium enema) –pictures of the large intestine that show polyps or other changes

Sigmoidoscopy – an examination of the rectum and lower colon using a lighted tube called a sigmoidoscope

Colonoscopy – examination of the rectum and entire colon using a lighted tube called a colonoscope

Polypectomy – the removal of a polyp during a sigmoidoscopy or colonoscopy

Biopsy – the removal of colon or rectal tissue to be tested for cancer cells

Treatment

Once colon cancer is found, staging tests are performed to find out if the cancer has spread and, if so, to what extent. Treatment depends on the stage of the cancer.

Treatments include:

Surgery (Colectomy) – the main treatement for colorectal cancer, surgical removal of the cancerous tumor and nearby colon or rectum tissue, and possibly nearby lymph nodes. In most cases, the doctor reconnects the healthy portions of the colon or rectum. If they cannot be reconnected, a temporary or permanent colostomy is necessary. Colostomy is a surgical opening through the abdomen into the colon through which body waste is collected in a special bag that is worn on the outside of the body.

Radiation Therapy (Radiotherapy) – the use of radiation to kill cancer cells and shrink tumors. Radiation is directed at the colon from a source outside the body.

Chemotherapy – the use of drugs to kill cancer cells. Chemotherapy may be given in many forms, including pill, injection, and via a catheter. The drugs enter the bloodstream and travel through the body killing mostly cancer cells, but also some healthy cells.

Biological Therapy (Biological Response Modifier Therapy) – the use of medications or substances made by the body to increase or restore the body's natural defenses against cancer.

Prevention

The cause of most colorectal cancer is not known. However, it is possible to prevent many colon cancers by finding and removing polyps that could become cancerous. Beginning at age 50, both men and women at average risk for the development of colorectal cancer should follow one of the five screening options listed below:

• Yearly fecal occult blood test or fecal immunochemical test

• Flexible sigmoidoscopy every 5 years

• Yearly fecal occult blood test or fecal immunochemical test plus flexible sigmoidoscopy every 5 years

• • Of the above options, the American Cancer Society prefers the third one.

• Double contrast barium enema (x-rays of the colon and rectum) every 5 years

• Colonoscopy every 10 years

People with any of the following risk factors should begin colorectal cancer screening earlier and/or undergo screening more often:

• A strong family history of colorectal cancer or polyps

• A known family history of hereditary colorectal cancer syndromes

• A personal history of colorectal cancer or adenomatous polyps

• A personal history of chronic inflammatory bowel disease

RESOURCES:

American Cancer Society
http://www.cancer.org

CancerCare
http://www.cancercare.org

References:

American Cancer Society website. Available at: http://www.cancer.org/docroot/home/index.asp.

National Cancer Institute website. Available at: http://www.cancer.gov/.