How To Reduce The Risk Of Colon Cancer

Colorectal cancer is one of the most common cancers in the world. About one in 20 people will develop cancer of the colon or rectum in their lifetimes. It also is the second leading cause of cancer deaths when men and women are considered together and is the third leading cause of cancer death among women.
The good news is that the disease is not only highly beatable and treatable, but also highly preventable. Regular screening and removal of polyps can reduce colorectal cancer risk by up to 90 percent. But unfortunately, fear, denial and embarrassment keep many people from being screened.

When colon cancer is caught and treated in stage I, there is a 74 percent chance of survival at five years. Once the cancer is larger and has spread to the lymph nodes, however, the five-year survival rate drops to 46 percent. If the cancer has already spread to distant parts of the body such as the liver or lungs, the five-year survival rate goes down to 6 percent.
The large intestine is the last section of the digestive tract and consists of the colon and rectum. The colon is four to six feet long, and the last seven to nine inches of it is called the rectum. After food is digested in the stomach and nutrients are absorbed in the small intestine, waste from this process moves into the colon, where it solidifies and remains for one or two days until it passes out of the body.
Sometimes the body produces too much tissue, ultimately forming a tumor. These tumors can be benign (not cancerous) or malignant (cancerous). In the large intestine, these tumors are called polyps. Polyps are found in about 30 percent to 50 percent of adults. People with polyps in their colon tend to continue producing new polyps even after existing polyps are removed.
There are several types of polyps, the most common being hyperplastic polyps, adenomatous polyps, sessile serrated polyps and malignant polyps. Hyperplastic polyps are typically not precancerous. Adenomatous polyps (also called "adenomas") and sessile serrated polyps may undergo cancerous changes, becoming adenocarcinomas. Malignant polyps are already cancerous.
Colon cancers develop from precancerous polyps that grow larger and eventually transform into cancer. It is believed to take about 10 years for a small precancerous polyp to grow into cancer. Therefore, if appropriate colorectal cancer screening is performed, most of these polyps can be removed before they turn into cancer, effectively preventing the development of colon cancer.
Besides adenocarcinomas, there are other rare types of cancers of the large intestine, including carcinoid tumors typically found in the appendix and rectum; gastrointestinal stromal tumors found in the connective tissue of the colonic or rectal wall; and lymphomas, which are malignancies of immune cells that can involve the colon, rectum and lymph nodes.
Risk Factors
The exact cause of colon cancer is unknown, but it appears to be influenced both by hereditary and environmental factors. People at an increased risk of colon cancer include those with either a personal or family history of colorectal cancer or polyps, individuals with a long-standing history of inflammatory bowel disease and people with familial colorectal cancer syndromes. Some of those at high risk may have a 100 percent chance of developing colorectal cancer.
Specific risk factors include:

• Personal History: A personal history of colorectal cancer, benign colorectal polyps which are adenomas or sessile serrated polyps, or chronic inflammatory bowel disease (e.g., ulcerative colitis and Crohn's disease) puts you at increased risk for colorectal cancer. In fact, people who have had colorectal cancer are more likely to develop new cancers in other areas of the colon and rectum, despite previous removal of cancer.
• Heredity: If one of your parents, siblings or children has had colorectal cancer or a benign adenoma, you have a higher risk of developing colorectal cancer. If two or more close relatives have had the disease, you also have an increased risk; approximately 20 percent of all people with colorectal cancer fall into this category. Your risk is even greater if your relatives were affected before age 60 or if more than one close relative is affected.
  
  Additionally, there are two genetic conditions—familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC)—that lead to colorectal cancer in about 5 percent of patients.
  
  • Familial adenomatous polyposis (FAP). People who have inherited the FAP syndrome may develop hundreds to thousands of polyps in their colon and rectum at a young age, usually in their teens or early adulthood. These polyps are all adenomas. By age 40, almost all patients with FAP will develop colon cancer if they don't have preventive surgery. Most people who have this syndrome begin annual colon examinations while in elementary school, and many choose to have their colon and rectum removed before cancer develops. FAP is rare, accounting for about 1 percent of all cases of colorectal cancer.
  • Hereditary non-polyposis colon cancer (HNPCC). Also known as Lynch Syndrome, HNPCC is a more common form of inherited colon cancer, accounting for about 3 percent to 5 percent of all colorectal cancer cases. While it is not associated with thousands of polyps, polyps are present and grow more quickly into cancer than in patients without HNPCC. Colon cancer in people with HNPCC also develops at a younger age than sporadic colon cancer, although not as young as in those with FAP.
    
    Cancers in patients with HNPCC tend to be fast growing and respond less to chemotherapy. The lifetime risk of colon cancer in people with HNPCC may be as high as 80 percent. People with HNPCC are also at an increased risk for other types of cancer, including cancer of the ovary, uterus, stomach, kidney and bladder.
  • MUTYH-associated polyposis (MAP): People with this syndrome, which is caused by mutations in the gene MUTYH, develop colon polyps that are destined to become cancerous if they are not removed. Their colonoscopy findings may be similar to FAP with hundreds to thousands of polyps or not. People with MUTYH are also at increased risk of cancers of the small intestine, skin, ovary and bladder.

There are some additional rare genetic mutations associated with colon cancer. These include Turcot syndrome, an inherited condition in which people are at an increased risk of adenomatous polyps (and thus, colon cancer) and brain tumors, and Peutz-Jeghers syndrome, a condition that leads to freckles around the mouth and sometimes on the hands and feet, as well as large polyps in the digestive tract and an increased risk of colon and other cancers at a young age.
In addition, there are several gene mutations found in Jews of Eastern European descent (Ashkenazi Jews) that increase colon cancer risk. The most common mutation, which is called the I1307K APC mutation, is found in 6 percent of American Jews.
If you have a history of adenomas or colon cancer or suspect you have a family history of the disease, you should discuss this with your health care professional because you may need to begin screening for the disease at a relatively young age. In some cases, you may wish to undergo genetic testing.

• Age: The risk of colorectal cancer increases with age. Ninety percent of new cases of colorectal cancer in the United States are in people over 50. Clinical studies indicate that when screened for the disease, African Americans tend to be diagnosed with colorectal cancer at a younger age than Caucasians.
• Race: African Americans are more likely to get colorectal cancer than any other ethnic group. Compared to Caucasians, African Americans are about 10 percent more likely to develop colorectal cancer. Unfortunately, they also are more likely to be diagnosed in advanced stages. As a result, African Americans are more likely to die from colon cancer than Caucasians. In 2007, the rate of death from colon cancer among African Americans was 44 percent greater than that among whites.
• Diet: Eating a diet high in processed meats (hot dogs and some lunch meats) and red meats (lamb, beef or liver) may increase your risk of developing the disease. Avoiding red meat and eating a low-fat diet rich in vegetables, fruit and fiber (e.g., broccoli, whole grains and beans) may reduce your risk of developing colorectal cancer. Some studies suggest that boosting calcium intake helps prevent colon cancer. Until further studies are done, men should keep their intake below 1,500 milligrams because of the increased risk of prostate cancer associated with high levels of calcium. Some research has also shown that vitamin D, which you can get from foods, sun exposure or a pill, can help lower colon cancer risk, but because of the increased risk of skin cancer with sun exposure, most health care professionals don't advocate getting more sun to reduce colorectal cancer at this time. Other studies suggest that taking a multivitamin that contains folic acid may lower colon cancer risk, but more study is needed in this area. There is some research suggesting that a diet high in magnesium may decrease colon cancer risk, especially in women. More research is necessary to find out if this link exists.
• Lifestyle: Regular exercise is a key weapon in the fight against colorectal cancer. Another significant risk factor in colorectal cancer is smoking. Get help quitting if you can't do it on your own. And keep your alcohol intake to one drink a day or less (two drinks a day or less for men).
• Obesity: Obesity is an epidemic in the United States and has been associated with many types of cancers, including colorectal cancer. There is a strong link between higher BMI (body mass index) and waist circumference and colon cancer risk in men and a weaker association seen in women. High levels of insulin and insulin-like growth factor may play a role in development of colon cancer in obese people. Weight loss has been shown to reduce the risk of colon cancer.

Screening Tests
The American Cancer Society recommends all women and men over the age of 50 who are at average risk of colorectal cancer undergo one of the following:

• A fecal occult blood test once a year. This test detects microscopic amounts of blood in the stool and only detects tumors that are bleeding. This must be performed on three separate bowel movements, and you should avoid nonsteroidal anti-inflammatory medications (NSAIDS) for seven days and vitamin C and red meat for three days before collecting the stool samples. Your health care professional provides the necessary materials to collect the stool specimens for simple testing at home or in the office. The stool should be collected before it is in the toilet water. A wooden stick is used to smear a small sample of stool onto the slots in the test card. You will get three test cards, which, when completed, you return to your health care professional. Your health care professional may recommend this test earlier than age 50 or more frequently if you are at high risk for colon cancer and/or polyps.
• A flexible sigmoidoscopy every five years. This examination allows the health care professional to inspect the rectum and lining of the left colon with a thin tube with a light and camera on the end. To prepare for the test, you may be asked to follow a special diet (such as drinking only clear liquids) for a day before the exam and to use enemas or laxatives to clean out your colon. The sigmoidoscope is inserted into the rectum while you lie on your left side. Sedative medication is not usually given for this procedure. This test is both diagnostic and therapeutic. However, it can only detect polyps or cancer accurately in the last two feet of the large intestine. Unfortunately, the sigmoidoscopy visualizes less than half the colon and misses about half of cancers and polyps that are close to becoming cancer in the first two to three feet of the colon.
• Fecal Immunochemical Test (FIT) every year. Similar to FOBT, FIT is a stool test that also detects hidden blood (occult) in the stool and must be performed every year. However, it tests for hidden blood in a different way than FOBT and has fewer false positive results. Some forms of FIT only require two stool specimens versus three for the FOBT, and neither vitamins nor foods will affect FIT results (these things can affect results of a FOBT); therefore, no dietary restrictions are necessary prior to collecting the stool samples. You perform the test in a similar manner as the FOBT. Similar to FOBT, the FIT test will not detect a tumor that is not bleeding, so a colonoscopy may be necessary for further screening or if cancer is suspected.
• Stool DNA at an uncertain frequency (manufacturer recommends every five years). A new screening approach, this test is available but not yet certified by the FDA. This test detects abnormal DNA shed by tumor cells into the stool and requires an entire stool sample. Studies are under way to determine how often the test should be done and how to increase its accuracy.
• A double contrast barium enema every five years. This test involves injecting barium (a liquid imaging agent that shows up during an X-ray) through the rectum into the colon, then taking X-rays of the colon. A health care professional injects the thick, chalky liquid through a small tube inserted into your anus. You may feel an urge to move your bowels, but should hold on while the X-rays are taken. After the X-rays finish, you can expel the liquid. To avoid becoming constipated afterward, you should drink plenty of fluids to flush the barium from your system. While the procedure can be uncomfortable, it is not usually painful. This test is only a diagnostic test. If abnormalities show up, a colonoscopy must be performed. The barium enema is not a very sensitive test and misses half of polyps that are larger than 1 centimeter.
• A colonoscopy every 10 years. Similar to the flexible sigmoidoscope, the colonoscope is a longer thin black tube that allows the health care professional to examine the entire large intestine. Preparation for the procedure requires drinking a laxative the day before the colonoscopy. Adequate preparation is critically important to enable the physician to visualize the entire lining of the colon. Leftover stool obscures the view of that portion of the colon and could lead to missing lesions. The ACS recommends getting a colonoscopy starting at age 50 for the average-risk person or if a FOBT or FIT shows blood in the stool. You typically receive a mild sedative during the procedure, so you should experience minimal discomfort. The procedure itself typically lasts 20 to 30 minutes.
  
  This test is both diagnostic and therapeutic. It detects polyps and cancers found anywhere in the colon. Any polyps or other growths found during this examination are usually removed and sent to a laboratory for examination. Medicare now covers this procedure every 10 years for people over 50 who are considered average risk for developing colon cancer and every two years for people at high risk. Women and men over 50 should have a colonoscopy at least every 10 years.
  
• CT colonography (virtual colonoscopy) every five years. This is a relatively new technique that uses a CT scan to create a three-dimensional image to evaluate the colon. It does not allow for a biopsy (tissue sampling) or polyp removal if any abnormalities are found. You must take a laxative the day before this test, similar to a colonoscopy, and if any abnormalities are found, you must undergo a colonoscopy. Most insurance companies do not cover virtual colonography as screening for colorectal cancer.

Most women find sigmoidoscopies and colonoscopies much more tolerable than they expect. Worrying about the process and undergoing the necessary preparation beforehand are often more unpleasant than the exam itself. Of the above-mentioned tests, colonoscopy is the preferred screening/prevention test, and FIT is the preferred test for patients who decline invasive cancer prevention tests.
Other tests that your health care provider might perform include:

• Digital rectal examination (DRE). Your health care professional inserts a gloved finger into the rectum to feel for any abnormalities. This simple test, which may be uncomfortable but usually is not painful, can detect many rectal cancers. However, even the longest of fingers are far too short to examine the full length of the large intestine. For this reason, other tests and examinations, such as the FOBT, flexible sigmoidoscopy and colonoscopy must be used. The rectal exam is not sufficient to screen for colon cancer.
• Genetic testing. The few hereditary cancer syndromes mentioned here are rare but are associated with mutations in specific genes. These mutations can be passed on to other family members. Thus, if your family is affected or may be affected by one of these syndromes, you may need to undergo genetic testing. If genetic testing and counseling are done properly, lives can be changed dramatically, both in terms of preventing colon cancer and lessening the psychological impact of knowing you are predisposed to the disease.
  
  Genetic testing for colon cancer raises many scientific and ethical issues. Although tests are available to identify the mutations that may predispose you to colon cancer, they are not absolutely positive predictors. Additionally, some health care professionals are not yet fully educated about the tests and may misinterpret the results.
  
  Thus, if you have a strong family history of colon cancer, you should be seen at a genetic screening center. Talk to your health care professional about the genetic screening process and how to locate such a center.
  

If there is a reason to suspect that you have colorectal cancer, your health care professional will take a complete medical history and perform a physical examination as part of an initial evaluation.
Symptoms
Symptoms of colorectal cancer include:

• Change in bowel habits (diarrhea, constipation or narrow stools for more than a few days)
• Urgency for a bowel movement or feeling like you need to move your bowels even if you just did
• Blood in the stool
• Stomach pain
• Weakness and/or fatigue

Contact your health care professional if you experience one or more of these symptoms.