Colon cancer is a malignant disease that develops in the lining of the large intestine (colon). The term colon cancer may also be referred to colorectal cancer—cancer of the colon and rectum. In general, colon cancer arises in benign polyps located in the inner surface of the colon. These polyps can take several years before turning into cancer.

Ending with the rectum, the colon is about six feet long and is the last segment of the intestine. Located between the small intestine and anus, the colon absorbs water and undigested foods. Feces are concentrated in the colon before being transported to the rectum, which assumes the role of fecal material storage awaiting defecation.

Colon Cancer Statistics  

Colon cancer is very common all over the world. Each year, over 940,000 new cases of colon cancer occur worldwide, killing approximately 655,000 people. The disease is very common in Western Europe, the USA, and Australia. Colon cancer is the second leading cause of death from cancer in the United States. It is estimated that 146,970 American residents (75,590 men and 71,380 women) were diagnosed with colon cancer in 2009 with nearly 49,920 men and women dying of it.

Age-adjusted incidence rate of colon cancer in 2002-2006 was 49.1 per 100,000 men and women per year. However, the incidence tends to vary by race and sex:

Incidence Rates by Race and Sex 

Colon Cancer Causes

Colon cancer occurs when there is an abnormal cell division in the colon. Contrary to the division of normal cells, these cancer cells have acquired certain characteristics that allow them to divide indefinitely and live longer than normal. During the course of the disease, even in the asymptomatic phase, some cancer cells can migrate from their place of origin to form metastases in nearby or distant organs. It is for this reason that screening for colon cancer should be started from age forty for people at risk and age fifty for individuals who are at low or risk. The following screenings must be done regularly as recommended by the American Cancer Society:

• fecal occult blood testing every year
• flexible sigmoidoscopy every five years
• double-contrast barium enema every five years
• colonoscopy every 10 years
• virtual colonoscopy (CT colonography) every five years.

The exact cause leading to the uncontrolled development of colon cells is not well known. However, several factors are suspected. Although genetics, sex, and age may contribute to the occurrence of colon cancer, environmental factors and lifestyle (including unhealthy diet) are the most common causes of colon cancer. They are responsible for about 80-90% of all colon cancers. Some lifestyle habits that can cause the development of colon cancer include: alcoholism, smoking, sedentary lifestyle, excessive consumption of red meat and foods containing highly saturated fats and proteins.

Colon Cancer Risk Factors 

Many factors such as diet, genetic diseases, and family history can increase your risk of colon cancer. Acknowledging these pathogenic factors helps scientists to develop methods to prevent the disease. Some risks factors suspected in the development of colon cancer include:

• Environment – Incidence of colon cancer is higher in developed countries like Western Europe, the USA, and Australia.
• Age – Almost 90% of colon cancer cases are registered among people over the age of fifty.
• Sex – Although the disease affects both men and women, men are more often victims of colon cancer.
• Certain intestinal diseases – Some inflammatory bowel disorders such as Crohn’s disease and ulcerative colitis may contribute to the development of colon cancer.
• Diabetes – Many studies have shown that people with Type 2 diabetes are more susceptible to getting colon cancer than non-diabetics.
• Unhealthy diet – A diet rich in red meat, fried meats, salami, sausages, and ham may increase the risk of colon cancer. The disease is less common in regions of the world where people eat little animal fat and many vegetable fibers. If you want to decrease your chances of colon cancer, it is necessary to eat lots of fruits and vegetables.
• Obesity – Being obese or overweight increases your risk of becoming a victim of several cancers, including esophageal cancer, colon cancer, breast cancer, endometrial cancer, andadrenal cell cancer (kidney cancer).

• Smoking – Smoking, including second hand smoke and chewing tobacco, have been factors in the development of colon cancer. Your risk is higher if you started smoking at a young age.

• Family history – If your family has a history of colon cancer or polyps, you are at a higher risk for having the disease. In fact, your chance is 35% higher than other people to develop colon cancer if your parents suffered from it.
• Genetics – Certain genetic medical conditions can lead to colon cancer. However, this is rare. Over 75% of cases of colon cancer have nothing to do with familial predisposition. The two most common forms of colon cancer that are related to genetic factors are hereditary nonpolyposis colorectal cancer (also called HNPCC or Lynch syndrome), which accounts for approximately 5% of colon cancers, and familial adenomatous polyposis (FAP), which is involved in about 1% of all colon cancer cases.
• Alcohol – There is a connection between heavy alcohol consumption and cancers of the digestive tract and other organs of the body like colon cancer, rectal cancer, esophageal cancer, laryngeal cancer, liver cancer, oral cancer, pharyngeal cancer, and even breast cancer. Moderate or occasional alcohol consumption presents no risk.
• Physical inactivity – In addition to cardiovascular disease and obesity, physical inactivity is one of the leading causes of colon cancer.

Colon Cancer Symptoms 

Colon cancer can remain asymptomatically for years in your colon before it produces symptoms. Meanwhile, the tumor continues to grow and damage your colon. When symptoms finally occur, the disease is already in advanced stages and chance of survival is very low. 

In general, if you have colon cancer, you will experience at least one of the following symptoms:

• vomiting
• anemia associated with fatigue
• blood in the stool
• unexplained weight loss
• have constant urge to defecate
• feeling that your bowel does not empty completely
• permanent discomfort characterized by stomach cramps, gas or pain
• persistent change in bowels habits such as alternation between constipation and diarrhea

Do not jump to any conclusion if you experience stool discoloration. Certain foods such as beets and red licorice can color your stool. The presence of blood in your stool does not mean you have colon cancer. Certain conditions such as hemorrhoids can lead to rectal bleeding.

Colon Cancer Complications  

Colon cancer is often subject to complications. The surgery does not guarantee that the cancer will not return. If the disease is untreated or if treatment does not work, the cancer can spread to the lymph nodes, then to the liver or lungs to form metastases. However, when chemotherapy and surgery are combined with a healthy lifestyle, your chance of survival is very high. If the cancer is detected at an early stage, you can be completely cured.

Colon Cancer Diagnosis 

Sometimes the cancer is detected during a routine colonoscopy performed for other medical conditions such as polyps. Colon cancer can also be found in someone who experiences blood in the stool and who has done a stool test.

Your chances of recovery are very high when the diagnosis is made early, but unfortunately, colon cancer is often detected very late after the disease has already damaged the tissues of the colon. If you experience symptoms of colon cancer, it is important not to make your own diagnosis; only a medical specialist can confirm the disease.

It is extremely important to see a health care provider if you experience symptoms of colon cancer for over three weeks. Your physician will perform medical procedures to detect the tumor and determine appropriate treatments. Most commons tests performed during a colon cancer diagnosis include:

Physical exam – To start the diagnosis, your doctor will question you about your medical history and the symptoms you experience. It is important to detail all the symptoms and times they occur. Tell your doctor about all recent changes occurring in your digestive system. If your doctor suspects cancer, a stool test will be recommended.

Stool test – Colon cancer can be detected early by less complicated diagnostic procedures. Although simple, the stool test can help your doctor detect presence of blood in your stool. In fact, even without signs of colon cancer, this test is recommended every two years as a means of screening for men and women aged 50-74 years. If the test reveals blood in your stool, other tests such as rectal examination, colonoscopy, sigmoidoscopy, barium enema, ultrasound, and CT scan will be performed to confirm the diagnosis.

Digital rectal examination (DRE) – A DRE is diagnostic technique during which your doctor inserts a gloved finger into your rectal cavity searching for abnormalities. The DRE helps your physician to detect abnormal growth in the rectum, but it can’t confirm if it is cancerous. Other medical techniques such as colonoscopy, barium enema, or sigmoidoscopy may be performed.  Digital rectal exam is painless; however, some patients find it uncomfortable.

Sigmoidoscopy – This invasive medical procedure allows your physician to examine the lining of your rectum and lower colon, using a sigmoidoscope – a hollow tube with a camera on the end. During the procedure, your health care provider inserts the tube through your rectum into the terminal section of your large intestine (sigmoid colon) to visualize and analyze it. In case of presence of growths (polyps), samples will be taken to be examined under microscope to look for cancer cells.

Barium enema – This radiological examination allows your doctor to visualize your lower gastrointestinal (GI) segment and confirm presence of polyps after filling the colon with a contrast material containing barium. During the procedure, the specialist injects the barium into your colon through a small tube placed in your anus. The barium travels throughout the colon, lining its walls in order to make them clearly visible on X-rays. This is a quick and painless test, but is less and less performed since the generalization of colonoscopy.

Colonoscopy – Acolonoscopy procedure allows the visualization of the inside of the colon in its entire length using a fiber optic flexible. During the exam, your physician inserts through your rectum a flexible tube with a light called endoscope. Unlike barium enema, colonoscopy allows your doctor to perform a biopsy of the tumor and removal of any polyps.

Other tests – Tests such as and ultrasound and computed tomography (CT) are used in the diagnosis of colon cancer. These techniques allow your doctor to determine the stage of the cancer and detect if it has spread to other organs (metastatic colon cancer) like the liver.

Colon Cancer Stages 

Once the cancer is found in your colon, it is important for your doctor to known its stage to determine the appropriate treatment. Your chances of recovery are closely related to the stage of the tumor at the diagnosis. Therapeutic strategy is also adapted to each stage of the cancer.

In general, stages of colon cancer include:

• Carcinoma in situ – Also called stage 0, carcinoma in situ is the earliest stage of the cancer; the tumor has not grown beyond the inner layer of the colon.
• Stage I – The cancer has grown within the inner layer of the colon without reaching the colon wall or rectum  
• Stage II – At stage 2, the cancer has affected the inner layer and the wall of the colon, but has not spread to nearby lymph nodes.
• Stage III – At stage 3 colon cancer is a serious condition. The cancer has affected the inner layer, the wall of the colon, nearby lymph nodes, but has not reached other parts of the body.
• Stage IV – At stage 4, the cancer has spread from the colon tissue to distant organs of your body such as liver and/or lungs.
• Recurrent – A cancer that has returned after treatment is considered as a recurrent cancer. In general, recurrent cancers are more difficult to be treated and have low survival rates.

Colon Cancer Treatment 

Colon cancer treatment depends on its location and stage at diagnosis. Whatever treatment is used, the earlier the cancer is detected, the more likely you are to survive. When colon cancer is diagnosed early (stage I for instance), recovery may be obtained in up to 90% of cases. However, colon cancer is often diagnosed after the tumor has already seriously damaged the colon.

The main treatment for colon cancer is surgery. Usually, the surgery aims at removing the tumor and surrounding lymph nodes (lymphadenectomy). Sometimes, the surgery is combined with chemotherapy or/and radiotherapy. Most of the times, chemotherapy is used if the cancer has spread to the lymph nodes, liver, or lung. Radiotherapy is performed if the excision of the tumor has been incomplete or in case a residual tumor is individualized on a vital organ. 

Surgical treatment 

Surgery for early-stage colon cancer – For early-stage colon cancer, surgery is performed to remove the tumor and surrounding tissue and lymph nodes. This treatment is effective in cases  where the cancer was discovered early enough. The surgical intervention can lead to a complete recovery if the cancer is strictly confined to the colon. Surgery may also be performed to prevent the occurrence of complications such as bowel obstruction or bleeding.

Surgery foradvanced colon cancer –  In the case of advanced colon cancer, removal of part of the colon containing the tumor and lymph nodes may be necessary (colostomy). A colostomy is a surgical diversion, which allows the surgeon to link your colon wall to your abdomen after a major surgical procedure. Thus, the bowel is diverted to the outside and feces can get into a specific apparatus called an artificial anus.

After the colostomy, your surgeon can restore the continuity of your intestines through an ileoanal anastomosis or ileorectal anastomosis:

• Ileo-rectal anastomosis – The ileum is connected to the rectum.

• Ileo-anal anastomosis – The ileum is connected directly to the anus and in this case the rectum is removed (proctectomy).

Complications – In some patients, the operation can lead to the following complications:

• infections
• pouchitis – inflammation of the ileal pouch
• risk of fistula due to rupture of the sutures.

Chemotherapy  

To treat your colon cancer, your surgeon can recommend weeks or months of chemotherapy, a systematic treatment that affects cells of your entire organism. The drugs travel in all parts of your body to destroy cancer cells by preventing them from multiplying. These drugs can be taken by injection, infusion, or by mouth. Unlike surgery, chemotherapy can be performed to treat advanced colorectal cancers that are associated with metastases in the liver and lungs. Chemotherapy is often associated with radiotherapy.

Side effects may include:

• fatigue
• nausea
• vomiting
• diarrhea
• constipation
• hair loss
• low blood cells count

Radiotherapy 

Radiotherapy is the use of high-energy radiation (energy X-rays or gamma rays) to kill cancer cells. During the therapy, your radiotherapist delivers precise doses of radiation in the tumor but spares surrounding healthy tissues, unlike chemotherapy. Radiation therapy may be performed before or after the surgery; however, in the treatment of colon cancer, it is often performed before the surgery to reduce the size of the tumor in order to make the surgery possible or more effective.

Although less toxic than chemotherapy, radiotherapy can also cause side effects, which tends to vary from person to another. The most common discomforts experienced after a colorectal cancer radiation therapy include:

• redness of the treated area
• urgent need to urinate
• burning sensation during urination
• erectile dysfunction (temporary).

Colon Cancer Survival 

Colon cancer prognosis depends greatly on the stage of the tumor at diagnosis. In general, when the cancer is detected early, you have a greater chance to survive. If your colon cancer is diagnosed at stage 1, your 5-year survival rate can be 90%.

According to the National Cancer institute (NCI), the overall 5-year relative survival rate for 1999-2005 was 65.2%. However, survival rates tend to vary by race and sex:

• 66.3% for white men
• 65.9% for white women
• 56.7% for black women
• 55.5% for black men

Death Rates by age  

From 2002-2006, the median age at death for cancer of the colon and rectum in the US was 75 years of age:

• 0.0%  died under age 20
• 0.6% between 20 and 34
• 2.4% between 35 and 44
• 8.0% between 45 and 54
• 15.2% between 55 and 64
• 22.6% between 65 and 74
• 30.8% between 75 and 84
• 20.4% 85+ years of age

Death Rates by Race 

The age-adjusted death rate was 18.2 per 100,000 men and women per year. These rates are based on patients who died in 2002-2006 in the US.

Colon Cancer Prevention   

Several methods can be used to help prevent the disease:

Aspirin – Aspirin seems to prolong the lives of patients with colon cancer. According to a U.S. study, aspirin can reduce by 29% the risk of recurrence of colon cancer. However, results vary from one person to another, and the prevention is effective for patients who adopt a healthy lifestyle and diet.

Early detection – To find early cancerous or precancerous polyps, it is now recommended for all people to undergo testing on a regular basis from the age of 40. The earlier the cancer is diagnosed, the higher your chances of recovery. In fact, it is estimated that screening for colon cancer can reduce up to 33% of colon cancer deaths among people aged 50 and over.

Lifestyle – These steps can help you not only prevent colorectal cancer, but also other types of cancer:

• Eliminate foods that can lead to the development of colorectal cancer like red meat, grilled sausage, smoked ham, and salami. If you cannot completely stop consuming them, eat them rarely and moderately.
• Quit smoking if you are smoker. Smoking is the source of a variety of diseases including colorectal cancer.
• Exercise at least three times a week.
• Consume alcohol moderately; heavy drinking increases your risk of developing colorectal cancer.
• Take vitamin D supplements in autumn and winter. If you are elderly or rarely get sun exposure, take vitamin D throughout the year
• Eat plenty of fruits, vegetables, and grains as these foods are rich in nutrients and antioxidants that keep not only your digestive tract healthy but also your whole body. It is shown in many studies that fruits and vegetables when consumed regularly and in great quantity, have beneficial effects in preventing and fighting against almost all types of cancer.