The intestine is a major part of the digestive system; its two major components are the small intestine and the large intestine, which includes three parts - the cecum, the colon, and the rectum. The colon's important role is to help the body absorb important nutrients and minerals, and to assist in flushing body waste through the rectum and anus.

The importance of the colon and rectum

The intestine is a major part of the digestive system; its two major components are the small intestine and the large intestine, which includes three parts - the cecum, the colon, and the rectum. The colon's important role is to help the body absorb important nutrients and minerals, and to assist in flushing body waste (in the form of stools) through the rectum and anus.

The term colorectal cancer includes colon cancer, which usually begins to form in the inner layers of the colon, and rectal cancer, which usually begins to form in the area of the rectum near the anus.
   

Warning signs

"During its early stages, colorectal cancer doesn't produce any symptoms, though it can be detected by a colonoscopy," Dr. Veerakit explains. "So it is recommended that once people reach the age of 50, they should have periodic screening tests."

Dr. Veerakit Apiratprachasin As the cancer develops further, it begins to produce symptoms including the following:

• Changes to normal bowel habits, such as a noticeable increase or decrease in frequency, diarrhea, constipation, or a feeling of not being able to empty the bowel completely;
• Red or dark blood in stool;
• Thinner-than-normal stools, abdominal discomfort, cramps or bloating;
• Unexplained weight loss;
• Nausea and/or vomiting (due to colon obstruction caused by malignant tumors);
• Fatigue and weakness resulting from occult bleeding caused by malignant tumors;
• Presence of an abdominal mass.

It's common for symptoms to vary among different individuals due in part to differences in the size or position of the cancerous tumor.
 

Who's at risk?

Despite the fact that it is hard to specify what causes colorectal cancer, the risk factors include:

• Age, especially beginning at the age of 50;
• Family history of colorectal cancer;
• Personal history of inflammatory bowel disease, especially for patients who've had the disease longer than seven years;
• Prior history of colorectal polyps;
• Inherited syndromes, including hereditary non-polyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP);
• Women with a personal history of ovarian, cervical or breast cancer;
• Obesity;
• Frequent consumption of high-fat foods and eating a diet lacking sufficient fiber, calcium and folate;
• Smoking, heavy alcohol consumption, and lack of exercise.

Screening and detection

"Like other types of cancer," says Dr. Veerakit, "colorectal cancer treatment outcomes are better when the disease is detected earlier. That's why people 50 years and older, and those considered to be at higher risk, should go for regular screenings. Don't wait until symptoms appear."

There are several methods to screen for colorectal cancer. Each has its own advantages and disadvantages. Doctors may recommend patients undergo more than one method to increase screening accuracy. The primary colorectal cancer screening tests are:

Fecal occult blood test - Visual examinations don't always detect the presence of blood in the stool. This laboratory test uses a chemical process to examine stool samples. When blood is present, the patient usually undergoes more detailed diagnostic testing.
 

• Sigmoidoscopy - During this procedure, the doctor inserts a flexible fiber-optic tube called a sigmoidoscope through the anus to examine the lower part of the colon and rectum. Prior to the procedure, the patient undergoes an enema to empty the bowel.
• Colonoscopy - This procedure is performed using a colonoscope, a flexible tube with a tiny video camera attached that is inserted through the anus. It allows the doctor to closely examine the entire colon and to immediately remove any polyps or other suspicious tissues. Patients are given general anesthesia prior to the procedure.
• Double-contrast barium enema - Barium is a chalk-like substance that enhances the quality of X-ray images. For this procedure, a barium-based liquid injected into the rectum helps produce X-ray images of the colon and rectum which are then checked for abnormalities. The procedure has a sensitivity rate of about 70 percent. If a polyp or other abnormality is suspected, a follow-up colonoscopy is usually performed to allow for removal of the polyp or other tissue samples to be tested for the presence of cancer cells.
• Digital rectal exam - Wearing a latex glove, the doctor inserts a finger into the anus to check for possible abnormalities in the anus and rectum. If an abnormality is found, the doctor usually recommends the patient undergo a colonoscopy for further evaluation.
• Virtual colonography - This non-invasive procedure uses advanced computer tomography scanning technology (CT scan) to produce detailed three-dimensional (3D) images of the colon, without the need for general anesthesia. The procedure has a high accuracy rate of nearly 90 percent. If any abnormalities are revealed - or in the small percentage of cases where an image may not be sufficiently clear to rule out the presence of an abnormality - the doctor usually recommends the patient undergo a colonoscopy for further evaluation.

When a patient's colorectal cancer screening shows no sign of potential problems, Dr. Veerakit generally recommends patients be screened again within three to five years. However, annual screening is recommended for patients who have been previously diagnosed with colorectal cancer and received successful treatment, to guard against its recurrence and the possibility of new cancers in other areas of the colon and rectum.

The stages of colorectal cancer

The progression of colorectal cancer is categorized by five stages:

• Stage 0: Cancer is present only on the innermost lining of the colon or the rectum - and is considered highly curable;
• Stage 1: The cancer has grown but is still confined within the inner layers of the colon or rectum; stage 1 cases have a high cure rate;
• Stage 2: The cancer spreads through the wall of the colon but remains curable;
• Stage 3: Cancer has spread to the lymph nodes. At this stage, the most effective treatment regimen to destroy the cancerous cells is usually surgery followed by chemotherapy;
• Stage 4: At this most advanced stage, the cancer has spread to the bones and/or vital organs such as the lungs and liver, making it nearly impossible to cure. Treatment at this stage may slow the cancer's progression and help improve the patient's quality of life.

Treatment options

The best treatment options for colorectal cancer depend largely on the stage of the disease's progression. In general, doctors usually recommend a combination of surgery and chemotherapy; in certain cases, treatment outcomes may be improved by adding radiation therapy to further help destroy cancerous tissues.

Colorectal cancer is particularly dangerous because it rarely produces symptoms during its early stages, making prevention and early detection critically important. "The key to lowering your colorectal cancer risk is to practice healthy lifestyle habits," Dr. Veerakit advises. "These include following a low fat, high fiber diet, getting regular exercise, avoiding smoking, and limiting alcohol consumption. Of course, these good habits help prevent other serious illnesses, too."
   
Did you know . . ?

• Colon polyps can develop into cancer without producing any symptoms, further demonstrating the importance of regular screening and early detection.
• While a family history of colorectal cancer is a risk factor for colorectal cancer, statistics show that about 75 percent of colorectal cancer patients have no family history of the disease.*
• The severity of colorectal cancer depends more on how deep the tumor penetrates through the colon wall, rather than the size of the tumor; a smaller tumor with deeper penetration is considered more dangerous than a larger tumor with less penetration.*
• Age is a key risk factor for colorectal cancer; over 90 percent of colorectal cancer cases occur in patients over the age of 50 (source: Chulabhorn Cancer Center).

*Source: "Myths & Facts About Colorectal Cancer," Richard Pazdur and Melanie E Royce, 2004.