Colorectal Cancer Colorectal cancer is malignant cells found in the colon or rectum. The colon and the rectum are part of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body (invade or metastasize).
Colorectal cancer is the second leading cause of cancer deaths in the United States. However, the number of new cases of colorectal cancer, and the number of deaths due to colorectal cancer, have decreased, which is attributed to increased sigmoidoscopic screening and polyp removal.
Anatomy of the Colon
The colon is the first 6 feet of the large intestine.
It has four sections:
The first section is called the ascending colon. It extends upward on the right side of the abdomen.
The second section is called the transverse colon since it goes across the body to the left side.
There it joins the third section, the descending colon, which continues downward on the left side.
The fourth section is known as the sigmoid colon because of its S-shape. The sigmoid
colon joins the rectum, the last 8 to 10 inches of the gastro-intestinal tract which, in turn,joins
the anus, or the opening where waste matter passes out of the body
Most colon and rectal cancers begin as small, noncancerous (beginning) clumps of cells called adenomatous polyps. Over time some of these polyps become cancerous.
Polyps may be small and produce few, if any, symptoms, so it's important to get regular screening tests to help prevent colorectal cancer. If signs and symptoms of cancer do appear, they may include a change in bowel habits, blood in your stool, persistent cramping, gas or abdominal pain.
Colorectal cancer is the second-leading cause of cancer-related deaths in the United States. Only lung cancer claims more lives. Each year, more than 135,000 Americans are diagnosed with colorectal cancer and 56,000 die.
Still, there's good news about colorectal cancer. Screening tests, along with a few simple changes in your diet and lifestyle, can dramatically reduce your overall risk of developing the disease.
Symptoms of colorectal cancer
The following are the most common symptoms of colorectal cancer. However, each individual may experience symptoms differently. People who have any of the following symptoms should check with their physicians, especially if they are over 40 years old or have a personal or family history of the disease.
A change in bowel habits such as diarrhea, constipation, or a change in consistency of the stool that lasts for more than a few days
narrow, pencil-thin stools
Rectal bleeding or blood in the stool on more than one occasion
Cramping or gnawing stomach pain
A feeling that your bowel doesn't empty completely
Unexplained weight loss
Decreased appetite
Vomiting
Weakness and fatigue
Jaundice (yellowish coloring) of the skin or sclera of the eye
The symptoms of colorectal cancer may resemble other conditions, such as infections, , inflammatory bowel disease and hemorrhoids. Bright red blood you notice on bathroom tissue may come from hemorrhoids or minor tears (fissures) in your anus, for example. Normally, hemorrhoids don't bleed consistently over a period of weeks. If your bleeding is prolonged, talk to your doctor.
It is also possible to have colon cancer and not have any symptoms. Always consult your physician for a diagnosis.
Stages of colorectal cancer
Staging helps determine how well you'll do and what treatments are most appropriate for you. In both cases, the size of your tumor isn't as important as how far your cancer has spread. People being treated for colorectal cancer have a five-year survival rate as high as 90 percent if treated in an early stage, before it has spread. When cancer has spread to lymph nodes or nearby organs, the survival rate drops to 65 percent or less. The stages are:
Stage 0
Your cancer is in the earliest stage. It hasn't grown beyond the inner layer (mucosa) of your colon or rectum. |
Stage I
Your cancer has grown through the mucosa but hasn't spread through the colon wall. |
Stage II
Your cancer has grown through the wall of the colon or rectum but hasn't spread to nearby lymph nodes. |
Stage III
Your cancer has spread to nearby lymph nodes but not to other parts of your body. |
Stage IV.
Your cancer has spread to distant sites, such as other organs — for instance to your liver or lung, to the membrane lining the abdominal cavity, or to an ovary. |
Recurrent.
This means your cancer has come back after treatment. It may recur in your colon, rectum or other part of your body.
Risk factors for colorectal cancer
Colorectal cancer can occur at any age, and no one is too young to develop colorectal cancer. However, about 90 percent of people with the disease are older than 50. Factors other than age that place you at a higher risk include:
Inflammatory intestinal conditions. Long-standing inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk.
Family history. You're more likely to develop colorectal cancer if you have a parent, brother, sister or child with the many family members have colon or rectal cancer, your risk is even greater. In some cases, this connection isn't hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
Familial adenomatous polyposis (FAP) is a rare hereditary disorder that causes you to develop hundreds of polyps in the lining of your colon and rectum, beginning in your teenage years. If these go untreated, you'll likely develop colon cancer by age 40. In most cases, genetic testing can help determine if you're at risk of FAP.
FAP also causes polyps to develop not only throughout your colon but also, in most cases, eventually in your upper intestine or duodenum. You may also develop noncancerous tumors in other parts of your body, including your skin (sebaceous cysts and lipomas), bone (osteomas) and abdomen (desmoid tumors).
Hereditary nonpolyposis colorectal cancer (HNPCC) is another hereditary disorder that can put you at high risk of developing colon or rectal cancer. Unlike FAP, however, you may have relatively few polyps.
If you're Jewish and of Eastern European descent, you may have an inherited tendency to develop colorectal cancer. This is particularly true of Ashkenazi Jews.
- Diet. Colorectal cancer may be associated with a diet low in fiber and high in fat and calories. Research is still occurring in this area. However, high-fiber, low-fat diets have additional health benefits apart from a potential connection to colorectal cancer prevention.
- A sedentary lifestyle. If you're inactive, you're more likely to develop colon cancer, although not rectal cancer. This may be because when you're inactive, waste stays in your colon longer. Getting regular physical activity may reduce your risk of colon cancer.
Causes of colorectal cancer
Cancer affects your cells, the basic units of life. 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 pre-cancerous polyps (adenomas, or adenomatous polyps) to form in the lining of your intestine. Over a long period of time — spanning up to several years — some of these polyps may become cancerous. In later stages of the disease, cancerous polyps may penetrate the colon walls and spread (metastasize) to nearby lymph nodes or other organs.
Polyps can occur anywhere in your large intestine, the muscular tube that forms the last part of your gastrointestinal (GI) tract. The colon comprises the upper 4 to 6 feet of your large intestine, and the rectum makes up the lower 8 to 10 inches. Your colon absorbs water, salt and other minerals from food and stores waste until it's eliminated from your body.
Polyps are either mushroom-shaped or flat and may be large or small. There are also several different types of colon polyps. Among the most common are:
- Adenomas. These polyps have the potential to become cancerous and are usually removed during screening tests such as flexible sigmoidoscopy or colonoscopy.
- Hyperplastic polyps. Often less than 1/4 inch in diameter, these polyps are rarely, if ever, a risk factor for colorectal cancer.
- Inflammatory polyps. These polyps may follow a bout of ulcerative colitis. Although the polyps themselves aren't a significant risk, having ulcerative colitis increases your overall risk of colon cancer.
Less than 10 percent of colorectal cancers are caused by inherited gene mutations.
People with a family history of colorectal cancer may wish to consider genetic testing. The American Cancer Society suggests that anyone undergoing such tests have access to a physician or geneticist qualified to explain the significance of these test results.
Lynch syndrome is due to a genetic defect that causes a predisposition to cancer. It's an autosomal dominant disorder, which means that you only have to inherit one copy of the defective gene to be affected. It affects both sexes equally. There are two types of this disorder:
- Lynch syndrome I, which increases the risk of colon cancer before age 50
- Lynch syndrome II, which increases not only the risk of colon cancer but also cancers of the ovary, pancreas, breast, bile ducts and bladder at an early age
Relatives of people who have Lynch syndrome are up to seven times more likely to develop colon cancer than are those without the gene defect. Genetic testing can detect the presence of the gene for Lynch syndrome. This may help you and your doctor decide on a preventive strategy, such as more frequent screenings for cancer. This strategy has been shown to decrease the risk of colon cancer. Some people with this gene have part of their colon removed.
People who have Lynch syndrome and develop cancer tend to have a better prognosis than do others who develop cancer. You may consider genetic counseling.
Screening for colorectal cancer
Perhaps most important to the prevention of colorectal cancer is having screening tests at appropriate ages. Because some colorectal cancers cannot be prevented, finding them early is the best way to improve the chance of successful treatment, and reduce the number of deaths caused by colorectal cancer.
The following screening guidelines can lower the number of cases of the disease, and can also lower the death rate from colorectal cancer by detecting the disease at an earlier, more treatable stage.
Screening methods for colorectal cancer, for people who do not have any symptoms or strong risk factors, include the following:
| Digital rectal examination (DRE) - a physician or healthcare provider inserts a gloved finger into the rectum to feel for anything unusual or abnormal. |
| Fecal occult blood test - a sample of stool is examined for blood. A test kit will explain how to take a sample at home. It is then returned to the physician's office to be examined. |
| Sigmoidoscopy - a slender, flexible, hollow, lighted tube is placed into the rectum allowing the physician to look at the inside of it and part of the colon for cancer or for polyps. |
| Colonoscopy - a long, flexible, lighted tube (much longer than a sigmoidoscope) about the thickness of a finger is inserted through the rectum up into the colon, allowing the physician to see the colon lining. |
| Barium enema with air contrast (Also called a double contrast barium enema.) - a fluid called barium (a metallic, chemical, chalky, liquid used to coat the inside of organs so that they will show up on an x-ray) is given into the rectum to partially fill up the colon. An x-ray of the abdomen shows strictures (narrowed areas), obstructions (blockages), and other problems. |
Most, if not all, colon cancers develop from polyps. Screening is extremely important for detecting polyps before they become cancerous. It can also help find colorectal cancer in its early stages when you have a good chance for recovery.
Like many people, you may be embarrassed by the screening procedures, worried about discomfort or afraid of the results. Try not to let these concerns stand in your way. Most procedures are only moderately uncomfortable, and working with a doctor you like and trust should help ease your embarrassment. If you question the results of your screening, ask for a second opinion. Keep in mind, however, that risks are associated with the more invasive screening procedures.
Screening procedures
- Digital rectal exam. In this office exam, your doctor uses a gloved finger to check the first few inches of your rectum for large polyps and cancers. Although safe and painless, the exam is limited to your lower rectum and can't detect problems with your upper rectum and colon. In addition, it's difficult for your doctor to feel small polyps.
- Fecal occult (hidden) blood test (FOBT). This test checks a sample of your stool for blood. It can be performed in your doctor's office, but you're usually given a kit that explains how to take the sample at home. You then return the sample to a lab or your doctor's office to be checked. The problem is that not all cancers bleed, and those that do often bleed intermittently. Furthermore, most polyps don't bleed. This can result in a negative test result, even though you may have cancer. On the other hand, if blood shows up in your stool, it may be the result of hemorrhoids or an intestinal condition other than cancer. For these reasons, many doctors recommend other screening methods instead of, or in addition to, fecal occult blood tests.
- Flexible sigmoidoscopy. In this test, your doctor uses a flexible, slender and lighted tube to examine your rectum and sigmoid — approximately the last 2 feet of your colon. Nearly half of all colon cancers occur in this area. The test usually takes just a few minutes. It can sometimes be somewhat uncomfortable, and there's a slight risk of perforating the colon wall.
- Barium enema. This diagnostic test allows your doctor to evaluate your entire large intestine with an X-ray. Barium, a contrast dye, is placed into your bowel in an enema form. During a double contrast barium enema, air is also added. The barium fills and coats the lining of the bowel, creating a clear silhouette of your rectum, colon and sometimes a small portion of your small intestine. This test typically takes about 20 minutes and can be somewhat uncomfortable. There's also a slight risk of perforating the colon wall. A flexible sigmoidoscopy is often done in addition to the barium enema to aid in detecting small polyps that a barium enema X-ray may miss, especially in the lower bowel and rectum.
- Colonoscopy. This procedure is the most sensitive test for colorectal cancer and polyps. Colonoscopy is similar to flexible sigmoidoscopy, but the instrument used — a colonoscope, which is a long, flexible and slender tube attached to a video camera and monitor — allows your doctor to view your entire colon and rectum. If any polyps are found during the exam, your doctor may remove them immediately or take tissue samples (biopsies) for analysis. This is done through the colonoscope and is painless. If you have adenomatous polyps, especially those larger than 5 millimeters in diameter, you'll need careful screening in the future.
A colonoscopy takes about a half-hour. You may receive a mild sedative to make you more comfortable. Preparation for the procedure involves drinking a large amount of fluid containing a laxative to clean out your colon — enemas are no longer necessary. Major risks of diagnostic colonoscopy include hemorrhage and perforation of the colon wall. But these risks are rare. Complications may be somewhat more frequent when polyps are removed.
- Genetic testing. If you have a family history of colorectal cancer, you may be a candidate for genetic testing. This blood test may help determine if you're at increased risk of colon or rectal cancer, but it's not without drawbacks. The results can be ambiguous, and the presence of a defective gene doesn't necessarily mean you'll develop cancer. Knowing you have a genetic predisposition can alert you to the need for regular screening. Still, you'll also want to consider the psychological impact of what the test may reveal. Knowing you may develop cancer affects not only your own life, but the lives of everyone close to you. Genetic testing for children is even more complex and problematic. It's best if you discuss all of the ramifications of genetic testing with your doctor or a medical geneticist.
- New technologies. In the future, new technologies, such as virtual colonoscopy, may make colon screening safer, more comfortable and less invasive. In virtual colonoscopy, you have a two-minute computerized tomography scan, a highly sensitive X-ray of your colon. Then, using computer imaging, your doctor rotates this X-ray in order to view every part of your colon without actually going inside. Before the scan, your intestine is cleared of any stool, but researchers are looking into whether the scan can be done successfully without the usual bowel preparation. Although virtual colonoscopy potentially is a tremendous step forward, it's not as accurate as regular colonoscopy and doesn't allow your doctor to remove polyps or take tissue samples. This test is also not widely available.
Another new test checks a stool sample for DNA from abnormal cells. In preliminary studies, the test has proved to be so accurate it may eventually eliminate the need for more-invasive examinations such as colonoscopy, at least in average-risk circumstances. A three-year clinical trial of this test by the National Cancer Institute is under way.
Screening guidelines
Beginning at age 50 for both men and women:
yearly fecal occult blood test, plus
flexible sigmoidoscopy every 5 years, or
colonoscopy every 10 years, or
double contrast barium enema every 5-10 years
People with any of the following colorectal cancer risk factors should begin screening procedures at an earlier age:
strong family history of colorectal cancer or polyps (cancer or polyps in a first degree relative younger than 60 or in two first degree relatives of any age)
family with hereditary colorectal cancer syndromes (familial adenomatous polyposis and hereditary non-polyposis colon cancer)
personal history of colorectal cancer or adenomatous polyps
personal history of chronic inflammatory bowel disease
Close relatives of patients with colon and rectal cancer (parents, brothers, sisters, children) are at increased risk for the disease. Because of this, periodic examination of the lining of the colon, using a colonoscope to detect small polyps, is advised. If polyps are promptly detected and removed, cancers cannot develop. Other factors which increase the risk of developing polyps or cancer include cancer occurring at an early age, and a personal history of breast or female genital cancer.
Treatment for colorectal cancer:
Specific treatment for colorectal cancer will be determined by your physician based on:
your age, overall health, and medical history
extent of the disease
your tolerance for specific medications, procedures, or therapies
expectations for the course of the disease
your opinion or preference
Surgical procedures
Surgery (colectomy) is the primary treatment for colorectal cancer. How much of your colon is removed and whether other therapies, such as radiation or chemotherapy, are an option for you depend on how far the cancer has penetrated into the wall of your bowel and whether it has spread to your lymph nodes or other parts of your body.
Your surgeon removes the part of your colon that contains the cancer, along with a margin of normal tissue to help ensure that no cancer is left behind. Nearby lymph nodes are usually also removed. Your surgeon is often able to reconnect the healthy portions of your colon or rectum. But when that's not possible, for instance if the cancer is at the outlet of your rectum, you may need to have a permanent or temporary colostomy. This involves creating an opening in the wall of your abdomen for the elimination of body wastes into a special bag. Sometimes the colostomy is only temporary, allowing your colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.
If you have colon surgery, side effects may include short-term pain and tenderness, and temporary constipation or diarrhea. If you have a colostomy, you may develop an irritation on the skin around the opening (stoma).
If your cancer is small, localized in a polyp and in a very early stage, your surgeon may be able to remove it during a colonoscopy. If the pathologist determines that the cancer in the polyp doesn't involve the base — where the polyp is attached to the bowel wall — then there is a good chance that the cancer has been completely eliminated. Some larger polyps may be removed using laparoscopic surgery.
If your cancer is advanced or your health poor, only a small portion of your colon or rectum may be removed. This isn't as effective as surgeries that remove more tissue, and doctors mainly do this to relieve blockages or bleeding.
Surgery is the most effective treatment for colorectal cancer. Even when all visible cancer has been removed, it is possible for cancer cells to be present in other areas of the body. These cancer deposits, when very small, are undetectable at the time of surgery, but they can begin to grow at a later time. The chance of recurrence depends on the characteristics of the original cancer and the effectiveness of chemotherapy, if needed, or other follow up treatment. Patients with recurrent cancers - if diagnosed early - may benefit, or be cured, by further surgery or other treatment.
Another good reason for postoperative follow up is to look for new colon or rectal polyps. Approximately one in five patients who has had colon cancer will develop a new polyp at a later time in life. It is important to detect and remove these polyps before they become cancerous.
Most recurrent cancers are detected within the first two years after surgery. Therefore, follow up is most frequent during this period of time. After five years, nearly all cancers that are going to recur will have done so. Follow u p after five years is primarily to detect new polyps, and can, therefore, be less frequent but advisable for life.
Radiation therapy
Radiation therapy uses X-rays to kill any cancer cells that might remain after surgery, to shrink large tumors before an operation so they can be removed more easily, or to relieve symptoms of colorectal cancer. Radiation is usually reserved for treatment of rectal cancer. The goal of therapy is to damage the tumor without harming the surrounding tissue. If your cancer has spread through the wall of the rectum, your doctor may recommend radiation treatments in combination with chemotherapy after surgery. This may help prevent cancer from reappearing in the same place Radiation may also be used to ease (palliate) symptoms such as pain, bleeding, or blockage. There are two ways to deliver radiation therapy, including the following:
External beam radiation uses a source outside the body to focus high-energy x-rays on the cancer.
Internal radiation therapy uses radioactive material that is placed next to or directly into the cancer.
Side effects of radiation therapy may include diarrhea, rectal bleeding, fatigue, loss of appetite and nausea.
Chemotherapy
Drugs (medications) are given into a vein or by mouth to kill cancer cells throughout the body. Studies have shown that chemotherapy after surgery can increase the survival rate for patients with some stages of colon cancer. Chemotherapy can also help relieve symptoms of advanced cancer. Your doctor may recommend chemotherapy if your cancer has spread. In some cases, chemotherapy is used along with radiation therapy. The drugs kill or cause damage to cancer cells, but may also damage normal cells. Hospitalization may be needed to monitor treatment and to control chemotherapy's side effects.
Possible side effects of chemotherapy include nausea and vomiting, mouth sores, fatigue, anemia, hair loss, diarrhea and increased likelihood of developing infections. If your doctor suggests aggressive treatment with multiple drugs, be sure you understand the side effects and risks as well as the potential benefits. Common side effects of chemotherapy depend on the type of drug used, the dosage, and the length of treatment. Side effects, and the degree to which they are experienced, differ. Most side effects disappear once treatment is stopped.
Treatment choices for the person with colon cancer depend on the stage of the tumor - if it has spread and how far. When the disease has been found and staged, your physician will suggest a treatment plan
Prevention of colorectal cancer
The most encouraging news about colorectal cancer is that you can reduce your risk by having regular screenings. You can also protect yourself by making a few simple changes in your diet and lifestyle. Although the exact cause of colorectal cancer is not known, the following suggestions may help save your life:
Eat plenty of fruits and vegetables. Fruits and vegetables contain vitamins, minerals, fiber and antioxidants, which may protect you from cancer. Try to eat five or more servings of fruits and vegetables every day. Look for deep green and dark yellow or orange fruits and vegetables, such as Swiss chard, bok choy, spinach, cantaloupe, mango, acorn or butternut squash, and sweet potatoes, as well as vegetables from the cabbage family, including broccoli, brussels sprouts and cauliflower. Lycopene, a nutrient found in tomatoes, may provide some minimal protection against cancer, but studies show that lycopene is helpful only if consumed as part of the whole fruit, and is unlikely to be beneficial when taken as a supplement. Also try to include legumes — including peas and beans — and soy foods, such as tofu or soy milk, in your diet.
Limit fat, especially saturated fat. People who eat high-fat diets may have a higher rate of colorectal cancer. Be especially careful to limit saturated fats from animal sources such as red meat. Other foods that contain saturated fat include milk, cheese, ice cream, and coconut and palm oils. Try to restrict your total fat intake to less than 30 percent of your daily calories, with no more than 10 percent coming from saturated fats.
Get recommended amounts of calcium and folic acid. Calcium and the B vitamin, folic acid, may help reduce your risk of colorectal cancer. Good food sources of calcium include skim or low-fat milk and other dairy products, broccoli, kale and canned salmon with the bones. Folate is the natural form of the B vitamin. It's found in certain foods naturally, including dark leafy greens such as spinach, and in pinto, kidney and navy beans, and some nuts and seeds. Folic acid is the synthetic form of the vitamin, and it's used in fortified breads, cereals, and supplements. Most multiple vitamins also contain both calcium and folic acid.
Eating foods rich in calcium and folic acid can have added benefits for women. If you are pregnant, or think you may become pregnant, getting enough folic acid in your diet reduces the risk of certain birth defects. Calcium also provides many benefits, including helping to prevent osteoporosis.
Limit alcohol consumption. Consuming moderate to heavy amounts of alcohol — more than two drinks a day — may increase your risk of colon cancer. This is particularly true if you have a close relative, such as a parent, child or sibling, with the disease. A drink is a 4- to 5-ounce glass of wine, a 12-ounce can of beer, or a 1.5-ounce shot of 80-proof liquor. Curbing alcohol consumption can reduce your risk, even if colon cancer runs in your family.
Stop smoking. Smoking can increase your risk of many different cancers. Talk to your doctor about ways to quit that may work for you.
Stay physically active and maintain a healthy body weight. Controlling your weight alone can reduce your risk of colorectal cancer. And staying physically active may cut your colon cancer risk in half. Exercise stimulates movement through your bowel and reduces the time your colon is exposed to harmful substances (carcinogens) that may cause cancer. Try to get at least 30 minutes of exercise on most days. If you've been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
Consider hormone replacement therapy. If you're a woman past menopause, hormone replacement therapy (HRT) may reduce your risk of colorectal cancer. Women who use HRT have a somewhat lower risk of colorectal cancer than women who don't use HRT. But not all effects of HRT are positive. Taking HRT as a combination therapy — estrogen plus progestin — can result in serious side effects and health risks. Work with your doctor to discuss the options and decide what's best for you.
