Colon Cancer


The large intestine comprises of the colon a muscular tube 5-6 feet long which absorbs water and nutrients from food and the rectum which is 6 inches long and stores the stool before its passage via the anus. Colorectal cancer is the third most common cancer in both men and women and the second most common cause of cancer-related death.

Colon cancer originates in the inner lining of the large intestine and more than 95% tumors are adenocarcinoma. Rarer types of colon cancer include carcinoid, gastrointestinal stromal tumor (GIST) and lymphoma.

Survival depends on the stage of colon cancer at the time of diagnosis. Death rate from colon cancer has been declining for the past 20 years because of early diagnosis and improved treatment. Staging of colon cancer- cancer confined to the colon is referred to as localized and the 5-year survival is 90%. If the cancer has spread to neighboring lymph nodes it is termed as locoregional and the 5-year survival is 70%. Spread to distant organs such as liver or lung is known as distant metastases and the 5-year survival falls to 12%.

Risk Factors

  • Family history of cancer
  • Familial adenomatous polyposis (FAP)
  • Hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome
  • Inflammatory bowel disease
  • Adenomatous polyps
  • Smoking

Symptoms

  • Rectal bleeding or blood in stool
  • Change in bowel habits- diarrhea or constipation lasting for several days
  • Abdominal pain
  • Feeling of incomplete evacuation after defecation
  • Loss of appetite or weight
  • Generalized weakness
COLON CANCER CELLS Courtesy, Urbain Weyemi, Christophe E. Redon, William M. Bonner, NCI Center for Cancer Research

COLON CANCER CELLS
Courtesy, Urbain Weyemi, Christophe E. Redon, William M. Bonner, NCI Center for Cancer Research

Screening

Colon cancer can be prevented by screening which identifies precancerous polyps. Screening should begin at age 50 in people with average risk and earlier when risk for colorectal cancer is increased. The current guidelines for colon cancer screening include the use of one of the following methods:

  • High sensitivity fecal occult blood test (FOBT) every year
  • Sigmoidoscopy every 5 years with FOBT testing between the endoscopy
  • Colonoscopy every 10 years

It is important to note that regardless of the screening test and schedule, any test which demonstrates an abnormality should be followed up by a colonoscopy.

Treatment

The choice of treatment depends on the stage of colon cancer and treatment options include surgery, chemotherapy, radiation therapy or a combination of these modalities.

Surgery
Surgery is the only potentially curative treatment for colon cancer. It involves removal of the colon in continuity with the adjacent lymph nodes and mesentery known as colectomy.

Chemotherapy
Chemotherapy is given after curative surgery for colon cancer (adjuvant chemotherapy) to eliminate occult cancer cells and improve survival. It may also be given prior to surgery in patients with distant metastases (neoadjuvant therapy).

Radiation therapy
Radiation may be used in combination with chemotherapy prior to surgery to shrink the tumor in locally advanced rectal cancer.

For more information visit: Colorectal Cancer | Cancer.net