Colon cancer is cancer of the large intestine (colon), the lower part of your digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they're often referred to as colorectal cancers.
Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time some of these polyps become colon cancers.
Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying polyps before they become colon cancer.
Signs and symptoms of colon cancer include:
- A change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool for more than a couple of weeks
- Rectal bleeding or blood in your stool
- Persistent abdominal discomfort, such as cramps, gas or pain
- A feeling that your bowel doesn't empty completely
- Weakness or fatigue
- Unexplained weight loss
Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms appear, they'll likely vary, depending on the cancer's size and location in your large intestine.
When to see a doctor
If you notice any symptoms of colon cancer, such as blood in your stool or a persistent change in bowel habits, make an appointment with your doctor.
Talk to your doctor about when you should begin screening for colon cancer. Guidelines generally recommend colon cancer screenings begin at age 50. Your doctor may recommend more frequent or earlier screening if you have other risk factors, such as a family history of the disease.
It's not clear what causes colon cancer in most cases. Doctors know that colon cancer occurs when healthy cells in the colon become altered. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But sometimes this growth gets out of control — cells continue dividing even when new cells aren't needed. In the colon and rectum, this exaggerated growth may cause precancerous cells to form in the lining of your intestine. Over a long period of time — spanning up to several years — some of these areas of abnormal cells may become cancerous.
Precancerous growths in the colon
Colon cancer most often begins as clumps of precancerous cells (polyps) on the inside lining of the colon. Polyps can appear mushroom-shaped. Precancerous growths can also be flat or recessed into the wall of the colon (nonpolypoid lesions). Nonpolypoid lesions are more difficult to detect, but are less common. Removing polyps and nonpolypoid lesions before they become cancerous can prevent colon cancer.
Inherited gene mutations that increase the risk of colon cancer
Inherited gene mutations that increase the risk of colon cancer can be passed through families, but these inherited genes are linked to only a small percentage of colon cancers. Inherited gene mutations don't make cancer inevitable, but they can increase an individual's risk of cancer significantly. Inherited colon cancer syndromes include:
- Familial adenomatous polyposis (FAP). FAP is a rare disorder that causes you to develop thousands of polyps in the lining of your colon and rectum. People with untreated FAP have a greatly increased risk of developing colon cancer before age 40.
- Hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC, also called Lynch syndrome, increases the risk of colon cancer and other cancers. People with HNPCC tend to develop colon cancer before age 50.
Both FAP and HNPCC can be detected through genetic testing. If you're concerned about your family's history of colon cancer, talk to your doctor about whether your family history suggests you have a risk of these conditions.
Factors that may increase your risk of colon cancer include:
- Older age. About 90 percent of people diagnosed with colon cancer are older than 50. Colon cancer can occur in younger people, but it occurs much less frequently.
- African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
- A personal history of colorectal cancer or polyps. If you've already had colon cancer or adenomatous polyps, you have a greater risk of colon cancer in the future.
- Inflammatory intestinal conditions. Long-standing inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk of colon cancer.
- Inherited syndromes that increase colon cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colon cancer. These syndromes include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, which is also known as Lynch syndrome.
- Family history of colon cancer and colon polyps. You're more likely to develop colon cancer if you have a parent, sibling or child with the disease. If more than one family member has colon cancer or rectal cancer, your risk is even greater. In some cases, this connection may not be hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
- Low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat and processed meats.
- A sedentary lifestyle. If you're inactive, you're more likely to develop colon cancer. Getting regular physical activity may reduce your risk of colon cancer.
- Diabetes. People with diabetes and insulin resistance may have an increased risk of colon cancer.
- Obesity. People who are obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
- Smoking. People who smoke cigarettes may have an increased risk of colon cancer.
- Alcohol. Heavy use of alcohol may increase your risk of colon cancer.
- Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colon cancer.
A diagnosis of cancer can be extremely challenging. Even when a full recovery is likely, you may worry about a recurrence of the disease. But no matter what your concerns or prognosis, you're not alone. Here are some strategies and resources that may make dealing with cancer easier:
- Know what to expect. Find out everything you need to know about your cancer in order to make treatment decisions. Ask your doctor to tell you the type and stage of your cancer, as well as your treatment options and their side effects. The more you know, the more confident you'll be when it comes to making decisions about your own care. Look for information in your local library and on reliable Web sites on the Internet. The National Cancer Institute (NCI) answers questions from the public. You can reach the NCI at 800-4-CANCER (800-422-6237). Or contact the American Cancer Society (AC at 800-227-2345.
- Maintain a strong support system. Friends and family can be your best allies as you face your cancer diagnosis. They often want to help, so take them up on offers to make meals or provide transportation to and from appointments. Sometimes the concern and understanding of a formal support group or other cancer survivors can offer unique emotional support. You may also find you develop deep and lasting bonds with people who are going through the same things you are. There are also support groups for the families of cancer survivors.
- Set reasonable goals. Having goals helps you feel in control and can give you a sense of purpose. But don't choose goals you can't possibly reach. You may not be able to work a 40-hour week, for example, but you may be able to work at least half time. In fact, many people find that continuing to work can be helpful.
- Take time for yourself. Eating well, relaxing and getting enough rest can help combat the stress and fatigue of cancer. Also, plan ahead for the downtimes when you may need to rest more or limit what you do.
Unfortunately, colon cancers can be well advanced before they are detected. The most effective prevention of colon cancer is early detection and removal of precancerous colon polyps before they turn cancerous. Even in cases where cancer has already developed, early detection still significantly improves the chances of a cure by surgically removing the cancer before the disease spreads to other organs. Multiple world health organizations have suggested general screening guidelines.
Digital rectal examination and stool occult blood testing
It is recommended that all individuals over the age of 40 have yearly digital examinations of the rectum and their stool tested for hidden or "occult" blood. During digital examination of the rectum, the doctor inserts a gloved finger into the rectum to feel for abnormal growths. Stool samples can be obtained to test for occult blood. The prostate gland can be examined at the same time.
An important screening test for colorectal cancers and polyps is the stool occult blood test. Tumors of the colon and rectum tend to bleed slowly into the stool. The small amount of blood mixed into the stool is usually not visible to the naked eye. The commonly used stool occult blood tests rely on chemical color conversions to detect microscopic amounts of blood. These tests are both convenient and inexpensive. A small amount of stool sample is smeared on a special card for occult blood testing. Usually, three consecutive stool cards are collected. A person who tests positive for stool occult blood has a 30% to 45% chance of having a colon polyp and a 3% to 5% chance of having a colon cancer. Colon cancers found under these circumstances tend to be early and have a better long-term prognosis.
It is important to remember that having stool tested positive for occult blood does not necessarily mean the person has colon cancer. Many other conditions can cause occult blood in the stool. However, patients with a positive stool occult blood should undergo further evaluations involving barium enema x-rays, colonoscopies, and other tests to exclude colon cancer, and to explain the source of the bleeding. It is also important to realize that stool which has tested negative for occult blood does not mean the absence of colorectal cancer or polyps. Even under ideal testing conditions, at least 20% of colon cancers can be missed by stool occult blood screening. Many patients with colon polyps are tested negative for stool occult blood. In patients suspected of having colon tumors, and in those with high risk factors for developing colorectal polyps and cancer, flexible sigmoidoscopies or screening colonoscopies are performed even if the stool occult blood tests are negative.
Flexible sigmoidoscopy and colonoscopy
Beginning at age 50, a flexible sigmoidoscopy screening tests is recommended every three to five years. Flexible sigmoidoscopy is an exam of the rectum and the lower colon using a viewing tube (a short version of colonoscopy). Recent studies have shown that the use of screening flexible sigmoidoscopy can reduce mortality from colon cancer. This is a result of the detection of polyps or early cancers in people with no symptoms. If a polyp or cancer is found, a complete colonoscopy is recommended. The majority of colon polyps can be completely removed by colonoscopy without open surgery. Recently doctors are recommending screening colonoscopies instead of screening flexible sigmoidoscopies for healthy individuals starting at ages 50-55.
Patients with a high risk of developing colorectal cancer may undergo colonoscopies starting at earlier ages than 50. For example, patients with family history of colon cancer are recommended to start screening colonoscopies at an age 10 years before the earliest colon caner diagnosed in a first-degree relative, or five years earlier than the earliest precancerous colon polyp discovered in a first-degree relative. Patients with hereditary colon cancer syndromes such as FAP, AFAP, HNPCC, and MYH are recommended to begin colonoscopies early. The recommendations differ depending on the genetic defect, for example in FAP; colonoscopies may begin during teenage years to look for the development of colon polyps. Patients with a prior history of polyps or colon cancer may also undergo colonoscopies to exclude recurrence. Patients with a long history (greater than 10 years) of chronic ulcerative colitis have an increased risk of colon cancer, and should have regular colonoscopies to look for precancerous changes in the colon lining.
Genetic counseling and testing
Blood tests are now available to test for FAP, AFAP, MYH, and HNPCC hereditary colon cancer syndromes. Families with multiple members having colon cancers, members with multiple colon polyps, members having cancers at young ages, and having other cancers such as cancers of the ureters, uterus, duodenum, etc., should be referred for genetic counseling followed possibly by genetic testing. Genetic testing without prior counseling is discouraged because of the extensive family education that is involved and the complicated nature of interpreting the test results.
The advantages of genetic counseling followed by genetic testing include: (1) identifying family members at high risk of developing colon cancer to begin colonoscopies early; (2) identifying high risk members so that screening may begin to prevent other cancers such as ultrasound tests for uterine cancer, urine examinations for ureter cancer, and upper endoscopies for stomach and duodenal cancers; and (3) alleviating concern for members who test negative for the hereditary genetic defects.
Diet and colon cancer to prevent colon cancer
People can change their eating habits by reducing fat intake and increasing fiber (roughage) in their diet. Major sources of fat are meat, eggs, dairy products, salad dressings, and oils used in cooking. Fiber is the insoluble, nondigestible part of plant material present in fruits, vegetables, and whole-grain breads and cereals. It is postulated that high fiber in the diet leads to the creation of bulky stools which can rid the intestines of potential carcinogens. In addition, fiber leads to the more rapid transit of fecal material through the intestine, thus allowing less time for a potential carcinogen to react with the intestinal lining.
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Thank you Healthshot for the information. Greatly appraeciated.