By Chris Woolston, M.S.
Most people are in denial about the possibility of getting any form of cancer. If they think about it at all, they're more likely to worry about lung or breast cancer than they are about cancer of the colon. Colon cancer is the second most deadly form of cancer after lung cancer. But it's one of the easiest diseases to detect, and in its earliest stages, it's also one of the most curable.
If you've been diagnosed with colon cancer, or if you're at risk for the disease, it's time to learn everything you can.
What is colorectal cancer?
Colorectal cancer is a cancer found in the colon or rectum. Like all forms of cancer, colorectal cancer gets its start when cells begin dividing uncontrollably. The cells then form tumors that can spread to other parts of the body.
Most colorectal cancers arise from small growths called polyps. Polyps come in two types, hyperplastic and adenomatous. Hyperplastic polyps are tiny and have no potential to turn cancerous. But adenomatous polyps can be dangerous, depending largely on size. Growths less than 5 millimeters across almost never cause trouble, but growths more than 2 centimeters across have a 50-50 chance of becoming cancerous within 10 to 15 years. Not all polyps are cancerous, but if they're adenomatous, they should still be removed and sent to the pathology lab for study.
How dangerous is colon cancer?
Lung cancer takes more lives each year, but colorectal cancer is the second leading cause of cancer death in the United States.
About one-third of all people with colon cancer and cancer in the rectum die from the disease within five years of diagnosis. As with any cancer, the longer the delay in treatment, the greater the danger. The good news is that deaths from this disease have declined compared with a decade ago, and early detection is apparently one reason.
If a doctor catches the cancer while it's still confined to the outer lining of the colon or rectum, you can probably look forward to a full recovery. If the cancer spreads to the muscle of the colon or rectum, you have a 75 percent chance to live at least another five years. In the worst-case scenario, the cancer can spread to the liver, bones, or lungs.
Who is at risk for colon cancer?
In general, colon cancer is not a young person's disease. In fact, more than nine out of 10 patients are over 50. However, some people have inherited conditions that make them vulnerable to colon cancer at a much younger age. For instance, people with familial adenomatous polyposis -- a rare condition in which hundreds of polyps form in the colon -- can develop colon cancer in their 20s. If left untreated, almost everyone with this problem will develop cancer by age 40.
Research reported in Science indicates that a mutation of a gene called BLM, most often found in people of Ashkenazi Jewish ancestry, may double or triple a person's risk of colorectal cancer. Scientists emphasize, however, that the causes of colorectal cancer are complex, and the gene mutation is only one possible factor.
If you've had colon cancer before, you're an obvious target for another bout of the disease. You're also more likely to develop the cancer if you have a history of polyps, Crohn's disease, or ulcerative colitis. Although researchers are not yet sure how big a role genes may play in colorectal cancer, you might have an increased risk if a close family member has the disease, according to a report in the New England Journal of Medicine. About 20 percent of all patients have a family history of the disease. Your risk is increased if a first-degree relative (i.e., parents who had cancer before age 60, or a sister or brother) has had colon cancer.
According to the American Cancer Society, having diabetes increases your risk of developing colorectal cancer by 30 percent.
Heavy smokers may also be especially vulnerable to colorectal cancer, in addition to lung cancer and heart disease. A study of more than 17,000 Swedish twins published in the International Journal of Cancer found that longtime smokers were three times more likely than nonsmokers to develop colorectal cancer. If you're a woman with a history of ovarian, uterine, or breast cancer, you also run a slightly increased risk of getting colorectal cancer.
Lifestyle can play a significant role in determining your risk of colon cancer. We all know that exercise is good for us, but when it comes to colon cancer, being active and staying fit appears to pay off. Dr. Anne McTiernan of the Fred Hutchinson Cancer Research Center in Seattle says that recent studies suggest that people who engage in regular, vigorous exercise can cut their risk of colon cancer by up to half. "We've observed an association between exercise and colon-cancer risk, even defined risk factors. Now we want to look at the mechanisms to explain these research results," said Dr. McTiernan.
If you're overweight, losing those extra pounds can help reduce your risk of colon cancer. A government study of over 13,000 people, published in the American Journal of Epidemiology, found that those with a body mass index (BMI) between 24 and 26 had an 86 percent greater risk of colon cancer when compared to those with a BMI of 22 or less. (BMI is a standard measurement to determine if a person's weight is appropriate to his height, and a BMI of 30 is considered obese.)
What are the symptoms of colorectal cancer?
Even as it grows and spreads, colorectal cancer is often a silent disease. Many people never suspect a problem until they undergo a routine screening test.
When colon cancer does cause symptoms, they are often easy to overlook. Many patients simply have constipation or diarrhea or bouts of both (symptoms that resemble those of a non-cancerous disorder known as irritable bowel syndrome). Other possible symptoms include bleeding from the rectum, blood in the stools, stomach cramps, and strong urges to have bowel movements when it's not necessary.
How is colorectal cancer diagnosed?
A thorough examination of the colon and rectum is the only way to detect polyps or cancer. Because colorectal cancer is both very common and very treatable in its early stages, these tests are some of the biggest lifesavers.
Two important tools for detecting polyps, cancer, and other colon diseases are flexible sigmoidoscopy and colonoscopy. In each procedure, a flexible, lighted tube (endoscope) equipped with a tiny camera at the end is inserted into the colon, giving the doctor a close look at the colon wall. Sigmoidoscopy explores the lower third of the colon, while a colonoscopy can screen the entire colon. While these tests are more invasive than some of the other methods your doctor may use, they are also more likely to detect cancer.
If you're over 50, your doctor may recommend a sigmoidoscopy every five years or a colonoscopy every 10 years. These exams may be combined with other, less invasive tests such as the fecal occult blood test or the fecal immunochemical test, both of which look for small traces of blood in your stool. Another test your doctor may recommend is a stool DNA test which checks for changes in DNA related to colon cancer.
Some doctors rely on barium enemas to check for polyps and cancer. In this exam, a radiologist takes x-rays of the colon after coating it with barium sulfate. The exam is relatively simple and inexpensive, but it isn't nearly as sensitive as colonoscopy. In one study, the x-rays missed 61 percent of polyps that were later found in a colonoscopy -- including a remarkable 52 percent of large polyps, the growths most likely to turn cancerous.
A new screening option, available at some medical centers, is virtual colonoscopy, a less invasive method which uses a computerized tomography (CT) machine to take images of the colon, rather than inserting an endoscope. Research on the effectiveness of virtual colonoscopy is ongoing.
As part of a routine rectal examination, your doctor may perform a digital rectal exam (DRE). During the DRE, your doctor uses a gloved finger to detect unusual growths in your rectum. However, the DRE is not a standard screening method for colorectal cancer since it may only detect growths in a small part of the colon.
What is the treatment for colorectal cancer?
If your doctor finds polyps with the potential to turn cancerous, they can often be easily removed by snaring them with an endoscope. Occasionally, a surgeon may use a laser to cut away small tumors in their earliest stages.
As the cancer grows, so does the seriousness of the operation. When attacking a larger tumor, the surgeon will remove an entire section of surrounding colon or rectal tissue to stop the spread of the disease. Afterward, he or she may be able to sew the healthy pieces of colon or rectum back together.
If your colon can't be reconnected, you will have to undergo a colostomy, an operation that creates an opening (stoma) on the outside of your body that will allow you to collect waste in a special bag. The surgeon may be able to reverse the operation once your colon has healed, but it could be permanent if you've lost a large amount of your bowel or if your rectum had to be removed.
Even if a colostomy is permanent, it shouldn't interfere with your life. A nurse can teach you how to learn to manage the bags so they don't show through your clothes or cause an odor.
If your cancer has spread beyond your colon, your surgeon probably can't remove all of the cancer cells. For this reason, you will need additional treatment to make sure these cells don't form new tumors. Your doctor may prescribe radiation treatment (large doses of high-energy rays) or chemotherapy (powerful medications) to kill the cancer. Some patients also receive alternative therapy, treatments that purport to help the immune system fight cancer. Before you start any of these treatments, talk to your doctor about all of your options. It's also a good idea to ask for a second opinion. Obviously, you'll want to find a treatment that gives you the best chance for recovery with the fewest side effects. Your doctor may even be able to enroll you in a clinical trial of new -- and potentially more effective -- therapies that haven't yet reached the market.
Can colorectal cancer be prevented?
Regular colon screening and removal of polyps will provide powerful protection against colon cancer. The American Cancer Society estimates that 90 percent of all colorectal cancer cases and deaths could be prevented by the timely use of screening tests, along with changes in diet and physical activity. If you're younger than 50, but have had polyps, inflammatory bowel disease, or someone in your family has had colorectal cancer, you should ask your doctor for a screening before you reach that age. Once you turn 50, the American Cancer Society suggests you follow one of the following screening test options:
- An annual fecal occult blood test (FOBT) plus flexible sigmoidoscopy every 5 years (the two tests in combination are more effective than either alone)
- A flexible sigmoidoscopy every 5 years
- An annual fecal occult blood test (FOBT)
- Colonoscopy every 10 years
- Double-contrast barium enema every 5 years
- CT colonography (virtual colonscopy) every 5 years
Any of these options can help catch problems before they get too serious -- check with your doctor to determine the best option for you.
A study reported at a meeting of the American Association for Cancer Research suggested that a simple baby aspirin may be an effective weapon against colon cancer for patients who have had precancerous polyps or colon cancers surgically removed. In the study of over 1,100 people, patients who took a baby aspirin a day reduced their risk of developing further precancerous polyps by 20 percent, while patients with colon cancer reduced their risk of recurrence by 40 percent.
Interestingly, the study found that a baby aspirin -- 81 milligrams -- was more effective than a standard aspirin, which is 325 milligrams. However, doctors don't advise a daily aspirin for everyone over 50 and the National Cancer Institute emphasizes that it is not clear whether aspirin lowers the risk of cancerous tumors. In fact, aspirin and other anti-inflammatory drugs like naproxen and ibuprofen carry their own risks, including heart attack, stroke, and bleeding in the stomach and intestines.
Researchers are also studying several vaccines that could help prevent colorectal cancer from coming back after treatment. Vaccines are currently available only in clinical trials.
Estimates vary, but there is no doubt that smoking is linked to colon cancer. So if you smoke, you have another good reason to quit.
As far as diet goes, eating lots of fruits and vegetables and limiting the amount of red meat you eat will lower your risk of colon cancer. The American Cancer Society (ACS) recommends eating five or more servings of fruits and vegetables a day, and eating whole grains rather than processed ones. Since obesity is also linked to colorectal cancer, the ACS says you should eat healthy, keep your weight down, and exercise regularly.
Limiting alcohol consumption is also a good idea for high-risk individuals. One French study of subjects who already had at least one colon polyp found that those who were heavy drinkers (those who consumed an average of 117 grams of alcohol a day for an average of 22 years) were likely to develop further precancerous polyps and colon cancer. (To get an idea of how much alcohol 117 grams is, 100 grams equals about 6 to 8 cans of beer, 6 to 8 glasses of wine, or 6 to 8 shots of hard liquor.)
The message to take home is simple: If you're a target for colon cancer or over age 50, get screened. If everybody followed that advice, a major killer would quickly lose its power.
Colon Cancer Alliance
1200 G Street, NW
Washington, DC 20005
202-434-8980 or 877-422-2030 Toll-free Helpline
The National Cancer Institute has a wealth of information about treatment and symptoms of colorectal cancer.
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