Cancer of the colon or rectum is also called colorectal cancer. In the United States, it is the fourth most common cancer in men and women. Caught early, it is often curable.

It is more common in people over 50, and the risk increases with age. You are also more likely to get it if you have

Polyps - growths inside the colon and rectum that may become cancerous
A diet that is high in fat
A family history or personal history of colorectal cancer
Ulcerative colitis or Crohn's disease

Symptoms can include blood in the stool, narrower stools, a change in bowel habits and general stomach discomfort. However, you may not have symptoms at first, so screening is important. Everyone who is 50 or older should be screened for colorectal cancer. Treatments include surgery, chemotherapy, radiation or a combination.

Colorectal cancer is the second most common visceral cancer in America and Europe. Nearly all cases are caused by adenocarcinomas and about 50% are lesions found in the rectosigmoid portion of the colon which adheres closely to the mucosal surface. The rest of the cases are caused by polyps.

Causes

The exact cause of the disease remains unknown. Studies have shown that it is common in areas of high economic development, which suggests a link to high-fat, highly-processed diets. Other factors which can increase one’s predisposition to colorectal cancer include:

Age over 40
Presence of other GI diseases
History of ulcerative colitis
Genetic tendency towards polyp formation
Presence of breast or gynecologic cancers

Signs and Symptoms

The most common signs include malaise and fatigue. Other findings result from local obstruction and in later stages, from direct extension to adjacent organs like the bladder, prostate, ureters, vagina, and sacrum. Later signs and symptoms will include:

Weight loss
Pain
Pale skin color
Malnutrition, weakness, drastic weight loss
Build-up of serous fluid in the abdominal wall
Liver enlargement
Widening of the lymphatic vessels, which can be painful

Diagnostic Tests

Only a tumor biopsy can give a definite diagnosis of cancer. For men and women aged 40 and older, other tests may be helpful. These include fecal occult blood tests every year, flexible sigmoidoscopy every 5 years, colonoscopy every 10 years or double contrast barium enema every 5 years. A fecal occult blood test is very useful at detecting blood in the stool, which is often a warning sign of rectal cancer.

A colonoscopy allows visual inspection of the colon up to the ileocecal valve and provides access for a polypectomy (removal of polyps) and biopsy of suspected lesions. A barium x-ray using dual contrast with air can locate lesions that are manually or visually undetectable, which should follow endoscopy since barium sulfate interferes with endoscopy.

Treatment

Surgery may be able to remove the cancerous tumor and adjacent tissues and affected lymph nodes. The type of surgery depends on the location of the tumor.

Chemotherapy is also used as an adjuvant therapy or for patients with metastasis, residual disease or inoperable tumors. Commonly-used drugs include 5-fluoruoracil, lomustine, mitomycin, methotrexate, vincristine, cisplatin, and levamisole.

Radiation therapy may also be done to induce tumor regression and can be used before or after surgery.

Prognosis

Colorectal cancer is very treatable with early detection and treatment. The five-year survival rate is 91% for those with colon cancer and 83% for rectal cancer patients. Survival is expected to drop with the spread of the disease.