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There is really no way to know for sure if you're going to get colorectal cancer. Certain factors can make you more likely to get colorectal cancer than another person. These are called risk factors. However, just having one or more risk factors does not mean you will get cancer. In fact, you can have many risk factors and still not get colorectal cancer, or you can have no known risk factors and still get it.
Is there a known genetic risk for colon cancer?
Hereditary risk for colon cancer is found in 10% to 20% of families where a member is diagnosed with colon cancer. One-third of those cases are related to very specific gene mutations. Lynch Syndrome, for example, represents a failure of cellular DNA repair genes that produces many gene mutations and leads to an increased risk for colon cancers and other cancers, such as endometrial cancer, to develop. A genetic risk is particularly suspected if someone is diagnosed with colon cancer at a much earlier age than is typical. In Lynch Syndrome, colon cancer might be diagnosed as early as age 30.
A more unusual and even more striking hereditary cancer syndrome is familial adenomatous polyposis (FAP) in which colon polyps and ultimately cancers can occur in teenagers. Other cancers—certain breast cancer, uterine cancer, ureter cancer—also may suggest an increased risk of colon cancer. A patient’s personal or family health history helps doctors make informed recommendations on initial screening and subsequent tests of the colon and other organ systems.
Stanford experts conduct an analysis of cancerous tumors removed from the colon looking for certain proteins that are markers for inherited risk of colon cancer; this analysis is called universal screening. If those proteins are found, then further genetic testing is conducted. The idea is to help families understand what their risk might be.
At Stanford, patients and their families will be seen at the Cancer Genetics Program for a detailed discussion of relevant family medical history. Not everyone who inherits such a genetic cancer risk will develop cancer. The human genome has 23,000 genes, with many genes and mutations remaining to be identified and understood. Scientists believe that environmental factors also may play a role. Learn more about cancer genetics.
Colon cancers can develop many genetic changes—and no one tumor is exactly like another. At Stanford, scientists are working to identify which genetic markers in a tumor will predict the effectiveness of a particular chemotherapy so a unique treatment can be designed for each patient. The Stanford Molecular Tumor Board has been organized to perform genomic profiling of metastatic GI and other cancers so novel genetic alterations can be identified, allowing targeted therapy of individual cancers.
Check your risk factors
See if any of the following statements in bold type apply to you. If any do, you may be at an increased risk for colorectal cancer. Some risk factors, such as having a family history of cancer or getting older, are out of your control. But some risk factors—whatyou eat, how much you weigh, whether you smoke, how much you drink, and how often you exercise--are factors you can control.
Every time you agree with one of the following statements, ask yourself this. "Am I doing all I can to control that risk factor?" Controlling it may seem hard, but your efforts can pay off in terms of your health and quality of life. Ask your doctors and your loved ones to help you think of ways you can lower your risk for colorectal cancer.
I am older than age 50.
The average age that people are diagnosed with colorectal cancer is 72. That doesn't mean you can't get the disease if you are younger. Even adolescents can get it. But the fact is that more than 90% of cases are found in people older than age 50.
People in my immediate family have had colorectal cancer.
One out of every five people with colorectal cancer has relatives who have had the disease. That's because family members share many of the same genes. It may also be because family members often have similar lifestyles. If your parents, brothers or sisters, or your children have had the disease, you're at a much higher risk than other people. This is especially true if your relative had the cancer before age 60.
I have had colorectal cancer before.
If you've had colorectal cancer before, you're at risk for developing it in another part of your colon or rectum. This is especially true if you had it before age 60.
I have had polyps in my colon or rectum.
Polyps are growths that can occur in your colon and rectum. They are common in adults older than age 50. Usually they're benign. That means they are not cancerous. However, some polyps can become cancer over time. That means that if you have a history of getting them, you may be more likely to get cancer. Polyps can be discovered and removed before they become cancer. This often happens during a routine screening test, such as a colonoscopy. You should talk with your doctor about how often to have one of these tests done.
I have the condition familial adenomatous polyposis, also called FAP.
FAP is a fairly rare inherited condition. It causes hundreds of polyps to form in someone who has it. These polyps often start to form by about age 16. Beginning at about age 20, the polyps could become cancerous. Most people with FAP develop cancer before age 40 unless they have preventive surgery. Learn more about familial adenomatous polyposis (FAP).
I have the condition hereditary nonpolyposis colon cancer, also called HNPCC.
About four out of every 100 cases of colorectal cancer are caused by HNPCC. This is a rare inherited condition. It causes polyps to form early in a person's life. But unlike FAP, which causes hundreds of polyps, this condition causes only a few. This condition can also cause other cancers such as endometrial cancer or cancer of the small intestine. Learn more about HNPCC.
Smoking raises a person's risk of colorectal cancer. There are many known cancer-causing agents, also called carcinogens, in cigarette smoke. Some are swallowed and can cause cancer in those parts of the digestive system they come in contact with. Some enter the blood and travel through your body to your intestines. If you smoke, your doctor may be able to help you find a stop-smoking program that can work for you.
Colorectal cancer is more common in people who are obese than people who are not. This is especially true for men. Researchers think that the extra weight increases insulin levels and that higher insulin levels cause polyps that can become cancerous. Being overweight is also associated with low levels of physical activity, and that is another risk factor.
I have type 2 diabetes.
People with type 2 diabetes are more likely to get colorectal cancer. Type 2 diabetes and colorectal cancer share some of the same risk factors, including obesity and physical inactivity. But even after taking these factors into account, people with type 2 diabetes still have a higher risk of colorectal cancer.
I drink more than one alcoholic drink a day.
If you drink more than one beer, glass of wine, or mixed drink a day, you're more likely to get colorectal cancer. And the more you drink, the higher your risk becomes. Researchers think that too much alcohol can change your DNA. Working with your doctor to stop drinking could lower your risk.
I eat a lot of red meat.
Red meat includes beef, pork, lamb, and veal. Studies show that if you eat a lot of red meat, you are at more risk for colorectal cancer than people who don't eat a lot of red meat. A healthy diet that lowers your risk for cancer is one low in animal fat that includes plenty of fruits, vegetables, and whole-grain products. Eating red meat well-done may even add to your risk. Researchers say that the high temperatures usually used to cook meat can produce certain cancer-causing compounds, also called carcinogens. Meat may also affect how your colon works by raising your levels of iron and producing compounds that damage cells.
I have inflammatory bowel disease, also called IBD.
There are several types of IBD. Ulcerative colitis and Crohn's disease are two. Chronic IBD causes long-term inflammation of your colon. This increases your risk for colorectal cancer. The longer you have one of these conditions, the more important it is to be screened for colorectal cancer at regular intervals.
I'm African American.
If you're African American, you're more likely to get colorectal cancer than members of other population groups. You're also more likely to die of the disease. It is not clear why these differences exist. One possible reason, researchers think, is a difference in access to screening and medical care. Another possible reason is differences in socioeconomic and lifestyle factors. Researchers are also studying the way tumors develop in African Americans.
If you're Jewish and of Eastern European descent (Ashkenazi), you may have a higher risk of getting colorectal cancer. Some evidence suggests a gene mutation is the reason. It isn't clear, though, that this genetic change is responsible for the increased number of colorectal cancers in Ashkenazi Jews.
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