Detailed Guide: Colon and Rectum Cancer
What Are the Risk Factors for Colorectal Cancer?
A risk factor is anything that increases your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, unprotected exposure to strong sunlight is a risk factor for skin cancer, and smoking is a risk factor for cancers of the lungs, larynx, mouth, throat, esophagus, kidneys, bladder, colon, and several other organs. Researchers have identified several risk factors that increase a person's chance of developing colorectal polyps or colorectal cancer.
Age: While younger adults can develop colorectal cancer, your chances of developing colorectal cancer increase markedly after age 50. More than 90% of people diagnosed with colorectal cancer are older than 50.
A personal history of colorectal cancer: If you have had colorectal cancer, even though it has been completely removed, you are more likely to develop new cancers in other areas of the colon and rectum. The chances of this happening are greater if you had your first colorectal cancer when you were age 60 or younger.
A personal history of colorectal polyps: If you have had an adenomatous-type polyp, you are at increased risk of developing colorectal cancer. This is especially true if the polyps are large or if there are many of them.
A personal history of chronic inflammatory bowel disease: Chronic inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is a condition in which the colon is inflamed over a long period of time. If you have chronic inflammatory bowel disease, your risk of developing colorectal cancer is increased. You should start being screened by colonoscopy 8 to 12 years after you were first diagnosed with IBD and testing should be repeated frequently (every 1 to 2 years). Often the first sign that cancer may be developing is called dysplasia. Dysplasia is a term that refers to cells that are no longer normal but they are not cancer yet. Inflammatory bowel disease is different than irritable bowel syndrome (IBS), which does not carry an increased risk for colorectal cancer.
A family history of colorectal cancer: Some cancers can “run in the family” because something in the environment has contributed to the development of cancer and/or because certain family members were born with, or inherited, an increased genetic susceptibility to cancer. While most colorectal cancers occur in people without a family history of colorectal cancer, those with a family history of colorectal cancer or adenomatous polyps in any first-degree relative younger than age 60, or in 2 or more first-degree relatives at any age are considered at increased risk for the disease. (First-degree relatives are defined as parents, siblings, and children.)
Familial disease
About 30% of people who develop colorectal cancer have disease that is familial. People who have a strong family history of colorectal cancer (as defined above), especially if the relatives are affected before the age of 60, are considered at increased risk of developing this disease. People with a family history of colorectal cancer need to talk with their doctor about beginning colorectal cancer testing at a younger age than age 50.
Inherited disease
About another 10% of people who develop colorectal cancer have an inherited genetic susceptibility to the disease. Approximately, 3% to 5% of colorectal cancers are associated with the inherited colorectal cancer syndrome, called hereditary non-polyposis colorectal cancer (HNPCC), or Lynch syndrome. Another 1% of colorectal cancer cases are associated with the inherited syndrome, called familial adenomatous polyposis (FAP).
Familial adenomatous polyposis (FAP) is a disease where people typically develop hundreds of polyps in their colon and rectum. Usually this occurs between the ages of 5 and 40. Cancer usually develops in 1 or more of these polyps beginning at age 20. By age 40, almost all people with this disorder will have developed cancer if preventive surgery is not done. FAP is sometimes associated with Gardner syndrome, a condition that involves benign (non-cancerous) tumors of the skin, soft connective tissue, and bones. About 1% of all colorectal cancers are due to FAP.
Hereditary nonpolyposis colon cancer (HNPCC) is another clearly defined genetic syndrome. It accounts for 3% to 5% of all colorectal cancers. This syndrome also develops when people are relatively young. These people have polyps, but they only have a few, not hundreds as in FAP. Women with this condition also have a very high risk of developing cancer of the endometrium (lining of the upper part of the uterus). Other cancers associated with HNPCC include cancer of the ovary, stomach, small bowel, pancreas, kidney, ureters (tubes that carry urine from the kidneys to the bladder), and bile duct.
Doctors have found that most families with HNPCC have certain characteristics:
At least 3 relatives have colorectal cancer.
Two successive generations are involved.
At least 1 relative had their cancer when they were younger than age 50.
At least 2 of the people are first-degree relatives.
These are called the Amsterdam criteria. If any of these hold true for your family, then you might want to seek genetic counseling. But even if your family history satisfies the Amsterdam criteria, it doesn’t mean you have HNPCC. Only about 60% of families who have the Amsterdam criteria have HNPCC. The other 40% do not; and although their colorectal cancer rate is higher than normal (about 2 times), it is not as high as that of people with HNPCC (about 6 times).
A second set of criteria for HNPCC, which has been recently revised, is called the Bethesda criteria. These are used to determine whether a person with colorectal cancer should have their cancer tested for genetic changes called microsatellite instability (MSI). These criteria include at least one of the following:
The person is younger than 50 years.
The person has or had another cancer (endometrial, stomach, pancreas, ovary, kidney or ureters, bile duct) that is associated with HNPCC.
The person is younger than 60 years and the cancer has certain characteristics seen with MSI when viewed under the microscope.
A first-degree relative has been diagnosed with a non-colorectal cancer often seen in HNPCC carriers (endometrial, stomach, pancreas, ovary, kidney, ureters, or bile duct) and is younger than 50 years.
The person has 2 or more second-degree relatives who had an HNPCC-related tumor at any age.
MSI testing is the first step in laboratory testing to identify people with HNPCC. If a patient meets Bethesda criteria and has a tumor with MSI, more genetic testing will be needed to confirm that there is a mutation of one of the HNPCC genes. Still, the majority of people who meet the Bethesda criteria do not have HNPCC. On the other hand, about 2% of people with colorectal cancer who do not meet any of these criteria still have HNPCC when they are tested.
Doctors should also be suspicious of HNPCC if, instead of colorectal cancer, the family members have other cancers associated with this gene mutation. These are endometrial cancers, ovarian cancers, small bowel cancers, or cancer of the lining of the kidney or the ureters. Still, 1 family member younger than age 50 must have been diagnosed with colorectal cancer before a diagnosis of HNPCC is considered.
Accurate identification of families with these inherited syndromes is important. Then doctors can recommend specific measures, such as screening and other preventive measures, at an early age. Because several types of cancer can be associated with inherited colorectal cancer syndromes, all people should check their family medical history for polyps or any type of cancer. Those who develop polyps or cancer should inform other family members. People with a family history of colorectal polyps or cancer should consider genetic counseling, to review their family medical tree and determine whether genetic testing may be right for them. This will help them to make decisions about getting screened and treated at an early age.
Ethnic background: Jews of Eastern European descent (Ashkenazi Jews) have a higher rate of colorectal cancer. Recent research has found a genetic mutation leading to colorectal cancer in this group. This DNA change is present in about 6% of American Jews. In one study, about 10% of colorectal cancers in Jews of Eastern European descent were associated with this mutation. This gene change is called the I1307K APC mutation. It isn't clear, though, that this genetic change is responsible for the increased number of colorectal cancers in Ashkenazi Jews.
A diet mostly from animal sources: A diet that is high in fat, especially fats from animal sources, can increase your risk of colorectal cancer. Over time, eating a lot of red meats and processed meats can increase colorectal cancer risk. The American Cancer Society recommends choosing most of your foods from plant sources and limiting your intake of high-fat foods such as those from animal sources. The American Cancer Society also recommends eating at least 5 servings of fruits and vegetables every day and several servings of other foods from plant sources, such as breads, cereals, grain products, rice, pasta, or beans. Many fruits and vegetables contain substances that interfere with the process of cancer formation.
Physical inactivity: If you are not physically active, you have a greater chance of developing colorectal cancer.
Obesity: If you are very overweight, your risk of dying from colorectal cancer is increased.
Smoking: Recent studies indicate that smokers are 30% to 40% more likely than non-smokers to die from colorectal cancer. Smoking may be responsible for causing about 12% of fatal colorectal cancers. Almost everyone knows that smoking causes cancers in sites in the body that come in direct contact with the smoke, such as the mouth, larynx, and lungs. However, some of the cancer-causing substances are swallowed and can cause digestive system cancers, such as esophageal and colorectal cancer. Some of these substances are also absorbed into the bloodstream and can increase the risk of developing cancers of the kidneys, bladder, cervix, and other organs.
Alcohol intake: Colorectal cancer has been linked to the heavy use of alcohol. While some of this may be due to the effects of alcohol on folic acid in the body, it still would be wise to avoid heavy alcohol use.
Factors with Uncertain, Controversial, or Unproven Effects on Colorectal Cancer
Race: African Americans have the highest incidence and mortality. The reason for this is uncertain.
Diabetes: People with diabetes have a 30% to 40% increased chance of developing colorectal cancer. They also tend to have a higher death rate after diagnosis.
Night-shift work: Results of one single study suggest working a night shift at least 3 nights a month for at least 15 years may increase the risk of colorectal cancer in women. The study authors suggested this might be due to changes in melatonin (a hormone that responds to changes in light) levels in the body. More research is needed to confirm or refute this finding, however.
The American Cancer Society and several other medical organizations recommend earlier screening for people with increased colorectal cancer risk. These recommendations differ from those generally recommended for people at average risk. For more information, speak with your doctor and refer to the table in the "Can Colorectal Polyps and Cancer Be Found Early?" section of this document.
http://www.cancer.org/docroot/home/index.asp
2006-07-27 19:30:02
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answer #8
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answered by leathersammie 4
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