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Gastroenterology
- Gastroenterology Introduction
- Colorectal Cancer screening questionnaire
- Colorectal cancer surveillance information
- Advice for people with Hepatitis C
Colon Cancer: Screening and Surveillance
Introduction
The colon is the part of the digestive system where the waste material is stored. The rectum is the end of the colon adjacent to the anus. Together, they form a long, muscular tube called the large intestine (also known as the large bowel).Cancer of the colon and rectum (Colorectal cancer) is a malignant tumor arising from the inner wall of the large intestine. Benign tumors of the large intestine are called polyps. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can be easily removed during colonoscopy, and are not life threatening. However, if benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. In fact, most of the cancers of the large intestine are believed to have evolved from benign (but pre-cancerous) polyps.
Cancer of the colon and rectum can invade and damage adjacent tissues and organs. Cancer cells can also break away and spread to other parts of the body (such as liver and lung) where new tumors form. The spread of colon cancer to distant organs is called metastasis of the colon cancer. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely.
Colorectal cancer is both preventable and curable. Colorectal cancer is preventable by removing pre-cancerous colon polyps. It is curable if early cancer is surgically removed before cancer spreads to other parts of the body. The National Polyp Study showed that in their surveillance program, the individuals who had their polyps removed experienced a 90% reduction in the incidence of colorectal cancer. The few patients in the study that did develop colon cancers were discovered at early curable stages. Since most colon polyps and early cancers are silent (produce no symptoms), colon screening and surveillance programs are important in reducing the incidence and mortality of colorectal cancer. Recommendations for cost-effective public screening and surveillance have been promulgated and endorsed by numerous societies including the American Cancer Society, the National Cancer Institute, American College of Gastroenterology, American Medical Association, American College of Physicians, etc.
Screening Recommendations
For individuals with average risk – The average risk of developing colorectal cancer over a person’s lifetime in the adult American population is approximately 6%. Fecal occult blood tests and flexible sigmoidoscopy examinations are recommended screening tests. These screening tests are designed to detect early polyps and cancers in order to decrease mortality from colorectal cancer. They are also affordable, easy to perform, and well tolerated by healthy individuals who have no symptoms.Fecal Occult Blood Tests – Fecal occult blood tests are special chemical tests performed on the stool samples to detect the presence of "occult blood. " These tests are usually begun at age 40 and then performed annually, accompanied by a digital rectal examination by a doctor.
Fecal occult blood tests are based on the observation that slow bleeding from colon polyps or cancers can cause chronic blood loss from the colon (sometimes causing iron deficiency anemia). Such bleeding is often not visible (occult) to the naked eye. Therefore, sensitive chemical tests are developed to detect blood traces in stool.
The testing consists of checking for chemical traces of blood in 3 stool specimens, collected on special cards by the individuals at home. To properly prepare for this examination, individuals are asked to abstain (for 3-5 days before stool collection) from certain foods, medications and vitamins that can interfere with the accuracy of occult blood testing. They include certain meats, vitamins (especially vitamin C), iron, aspirin, and other anti-inflammatory medicines or NSAIDs (medications, such as ibuprofen, used in treating arthritis and other painful inflammatory conditions).
An individual whose stool specimen tests positive for blood then undergoes a colonoscopy examination of the entire colon to exclude colon polyps, cancers, or other bleeding abnormalities (such as abnormal blood vessels and colitis). The majority (greater than 90%) of the polyps detected can be removed painlessly and safely during the COLONOSCOPY examination. Polyps so removed are later examined by a pathologist under the microscope. Individuals with pre-cancerous polyps have higher than average risk of colon cancer, and are advised to return for periodic surveillance colonoscopies (see below). Colon cancers so detected are usually removed surgically, especially if the cancer has not already spread to other parts of the body. Pre-cancerous polyps that are too large or technically not possible to remove during colonoscopy are usually also removed surgically. Several studies have shown that fecal occult blood testing can reduce death rates (mortality) from colorectal cancer by 30-40%.
If no colon abnormalities are found in an individual whose stool is positive for occult blood considerations are then given to examining the stomach and the small intestines for sources of blood loss.
Flexible Sigmoidoscopy – Flexible sigmoidoscopy is a flexible viewing tube with a light at the end. It is used by the doctor to examine the rectum and the part of the left colon adjacent to the rectum. It is a shorter version of COLONOSCOPY. Approximately 50% of colorectal cancers and polyps are found to be within the reach of a flexible sigmoidoscope. Individuals of average risk are recommended to undergo a flexible sigmoidoscopy beginning at the age 50, and then every 3-5 years. If polyp(s) are found during a flexible sigmoidoscopy examination, a total colonoscopy is then recommended to remove these polyp(s), as well as to remove any additional polyps in the remaining parts of the colon. The polyps so removed are examined with a microscope by a pathologist. Individuals with pre-cancerous polyps (adenomas and villous adenomas) have higher than average risk of developing colon cancer, and are recommended to return periodically for surveillance colonoscopies (see below).
Surveillance Recommendations
For individuals with higher than average risk – A number of individuals are at a greater risk for developing colorectal cancer because of a family history of colon cancer, long standing history of chronic ulcerative colitis, rare hereditary forms of colorectal cancer, or previous history of colon polyps or cancer. Periodic surveillance colonoscopies are recommended for these individuals to remove pre-cancerous polyps to prevent colon cancer, and/or to detect early cancers.Patients with History of Colon Polyps – Patients with a history of colon polyp(s) removed can slowly develop subsequent polyps over years. Therefore, periodic infrequent surveillance colonoscopies are recommended. In individuals with only one completely excised pre-cancerous polyp, the usual recommendation is to repeat the colonoscopy at 3 years. If the 3 year colonoscopy shows no polyp recurrence, then the interval between colonoscopies is extended to 5 years.
Sometimes, doctors are not confident that all polyps have been completely removed. Examples include individuals with multiple pre-cancerous polyps, polyps that are technically difficulty to completely excise, or less than optimal visualization of the colon due to inadequate cleansing of the colon. Under these circumstances, the decision regarding interval between surveillance colonoscopies is best arrived at jointly between the patient and the doctor.
Patients with History of Colorectal Cancer – Individuals who have undergone colon cancer surgery are at higher risk of developing another colon cancer in the future. They are usually recommended to undergo a repeat colonoscopy at 6 months to a year and then every 3 years hereafter.
Early detection and treatment of future polyps and early cancers can significantly improve chances of survival. The annual testing of stool for occult blood continues.
Patients with Ulcerative Colitis – Patients with long standing ulcerative colitis also have higher risk of developing colorectal cancer. The risk of developing colon cancer is proportional to the duration of disease and to the extent of colon involved by colitis. Thus, patients with chronic ULCERATIVE COLITIS involving the entire colon should have a colonoscopy every 1-2 years after having the colitis for 10 years or more. During the procedure, biopsies are taken from the colon to look for early microscopic precancerous changes in the cells. If precancerous cell changes are detected, colonoscopy is repeated in 3 months. If still present, doctors may approach the patient regarding surgically removing the colon to prevent colon cancer. If the colitis is limited to only the left colon, the same surveillance program is started at 15 years after the onset of colitis.
Family History of Colorectal Cancer – Colorectal cancer may run in families. Colon cancer risk to an individual is even higher if more than one immediate family member (parents, siblings or children) has had colorectal cancer, and/or the family member developed the cancer at a young age (younger than 55 years). Under these circumstances, individuals are recommended to undergo a colonoscopy every three years starting at an age that is 7-10 years younger than the youngest member with the cancer.
If only one immediate family member developed colorectal cancer at an advanced age, the colon cancer risk to the individual is still higher than average, but not as high as two immediate members, and early development of colon cancer among the relatives. Whether and when to perform screening colonoscopies in these individuals are best decided jointly by the patients and their doctors.
Other Groups in Need of Surveillance
There are other rare conditions that can increase the risk of colorectal cancer. These conditions are often hereditary, such as familial polyposis, familial nonpolyposis syndromes, the cancer family syndrome, hereditary site-specific colon cancer, etc. While uncommon, these conditions require specialized and complex surveillance and treatment. Individuals suspected of having these familial conditions should consult their doctors, a Gastroenterologist or an Oncologist (specialist in cancer) for proper treatment and close surveillance.Summary
Colon cancer is both preventable and curable. Colon cancer is preventable by removing precancerous colon polyps. It is curable if early cancer is surgically removed before cancer spreads to other parts of the body. Therefore, if screening and surveillance programs were practiced universally there would be a major reduction in the incidence and mortality of colorectal cancer.Ongoing genetic research will help doctors better understand the genetic basis of colorectal cancer formation. Future genetic blood tests or stool cell tests may also help with cancer screening. Other screening programs are currently being evaluated. One such screening program involves colonoscopy at age 50-55 and repeated once, in 10 years or so, instead of periodic sigmoidoscopies. Regardless of what new screening methods will become available, viewers should remember to discuss with their doctors colon cancer screening and/or surveillance as related to their own particular situations.
Gastroenterology Introduction
Colorectal Cancer screening questionnaire
Colorectal cancer surveillance information
Advice for people with Hepatitis C