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The lifetime probability of colon cancer is approximately 6% (i.e. 1 in every 20 people will be diagnosed with colon cancer). It is the third most common diagnosed cancer and the second leading cause of cancer-related death. In fact, 102,900 new cases of colon cancer are diagnosed and 51,370 colon cancers deaths are reported each year in the U.S. alone.
Most patients suffering from early staged colon cancer are asymptomatic. It is for this reason why colon cancer screening is highly recommended. The most common symptom found in colon cancer patients is bleeding during bowel movement. Other symptoms include: changes in bowel habits, persistent diarrhea or constipation, narrowing of the stool, abdominal pain and unexplained weight loss.
Like most cancers, there are measures patients can take to reduce their risk of developing colon cancer. The best way to reduce colon cancer risk is a healthy and proper diet. It has been shown that high fiber and low-fat diets are associated with a reduced risk. It is recommended that an individual consume 25-35 grams of fiber each day. Moreover, it is recommended to drink at least 8 glasses of non-caffeine, not sweetened fluids. In addition to a healthy diet, individual should maintain a healthy lifestyle and remain active. Following recommended screening procedures has also been shown to reduce patient population who is affected by colon cancer.
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Identifying patient populations at risk of colon cancer
Like all cancers, there are factors that influence the risk of developing colon cancer. Identifying the patient population who is affected by colon cancer can help reduce the incidence of colon cancer and reduce the burden this disease has on society. Population groups that have been identified to be at an elevated risk of developing colon cancer are briefly discussed below:
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Cancer risk in the elderly population
Advanced age is a common risk factor for most malignancies. While there have been reports of colon cancer in all age groups, more than 90% of all colon cancers are reported in patients over the age of 40 years. Of these patients over the age of 40 years, most diagnosed colon cancers are found within the ages of 50-60 years. Moreover, approximately 1.5% of all men over 60 years of age will develop a form of colon cancer sometime within the next 10 years. This means that 1 or 2 out of every 100 60 year old men will be diagnosed with colon cancer before their 70th birthday.
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Colon cancer runs in the family
Patients with a first-degree relative are at an increased risk of developing colon cancer. It has been shown that individuals with one or two relatives who have or had colon cancer are at a 2 fold risk of colon cancer. Causal explanations for the high incidence of colon cancer in families include:
- Genetic mutations – APC gene mutations have been shown to be associated with an increased risk of colon cancer
- Environmental influences – Family members are exposed to similar environmental stimuli, some of which may be oncogenic
- Interaction between genetic and environmental factors – Genes passed on through families can predispose members of that family to oncogenic environmental factors
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Patients with ulcerative colitis may be a risk
Ulcerative colitis is a disease that causes inflammation and sores, called ulcers, in the lining of the rectum and colon. It has been associated with a patient population who is affected by colon cancer in an elevated manner compared to the general population. In fact, approximately 5% of ulcerative colitis patients develop colon cancer. This elevated risk is influenced by the duration of the condition and the amount of colon damage. It has been shown that if the entire colon is affected patients are at a 32 times increased risk of developing colon cancer.
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Crohn`s disease and colon cancer
Approximately 1.2% of Crohn’s disease patients are diagnosed with a form of colon cancer. This represents a 20 times greater risk than the normal population. Another study demonstrated that an approximately 4-fold increase in the risk of colon cancer in patients suffering from Crohn’s disease. Moreover, in certain populations (Asian) where the incidence of Crohn’s disease is augmenting, the incidence of colon cancer is also increasing. It is important to note that Crohn’s disease is considered a risk factor for cancer in general and is not specific for colon cancer. In fact, studies have reported an increased risk of myeloid and lymphoid malignancies, as well as a 15-fold increased risk of carcinoid tumors in patients suffering from Crohn’s disease.
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FAP as a risk factor for colon cancer
Familial adenomatous polyposis (FAP) is an autosomal dominant disease which affects approximately 1 in every 8000 births. The development of FAP is closely linked to mutations in the APC gene, a gene that has been shown to be mutated in some colon cancers. In fact, APC mutations have been found in the most sporadic colon carcinomas. It accounts for less than 1% of all colon cancers. However, the risk of developing cancer in patients with APC mutations or FAP is close to 100%. This risk can be reduced by early screening followed by a prophylactic colectomy.
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Hereditary nonpolyposis colorectal cancer
Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by either a germline mutation in a mismatch repair gene or an association with tumors exhibiting MSI. It is characterized by an increased risk of a variety of cancer, including colon cancer. Other cancers that have been shown to be linked to HNPCC include: endometrium, ovary, stomach, small intestine, liver, upper urinary tract, brain and skin. HNPCC is associated with an earlier onset of colon cancer, with an average age of diagnosis of 44 years. Moreover, it is associated with an approximately 80% lifetime risk of colon cancer. Of these cancers, two thirds of them occur within the proximal colon. HNPCC-related colon cancers are characterized by distinct properties which include: poor differentiation, tumor-infiltrating lymphocytes, mucin and signet ring histology. Even if it is highly unexpected due to their poorly differentiated state, if colon cancers are matched stage for stage, HNPCC-related colon cancer is associated with a better prognosis compared to sporadic colon cancers.
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American Cancer Society - http://www.cancer.gov/cancertopics/types/colon-and-rectal
Centre for Disease Control and Prevention - http://www.cdc.gov/cancer/colorectal/statistics/age.htm
Temitope KO et al. Family history of colon cancer: What does it mean and how is it useful? Am J Preventive Med. 2003; 24:170-176.
National Institute of Health - http://digestive.niddk.nih.gov/ddiseases/pubs/colitis/
Freeman HJ. Colorectal cancer risk in Crohn`s disease. World J Gastroenterol. 2008; 14:1810-1811.
Al-Sukhni W., Aronson M., Gallinger S. Hereditary colorectal cancer syndromes: familial adenomatous polyposis and Lynch syndrome. Surg Clin N Am 2008; 88:819-844.
Kohlmann W., Gruber SB. Hereditary non-polyposis colon cancer. Gene reviews. 2006.