Colon cancer, like rectal cancer, is a part of the group of bowel cancers that originate in the large bowel (contains caecum, colon and rectum). Together they are often referred to as colorectal cancers. Most cases of colorectal cancers begin as small clumps of cells called polyps, which are benign (non-cancerous). Over a period of time, some of these polyps go on to become malignant (cancerous).
Approximately 80% of bowel cancers are diagnosed in people older than 60 years of age. It is the 3rd most commonly diagnosed cancer after skin and breast.
CAUSES AND RISK FACTORS
Factors that increase your risk of getting bowel cancer include:
Age: around 80% of people diagnosed with bowel cancer are over 60.
Diet: a diet high in fibre and low in saturated fat could reduce your bowel cancer risk. A diet high in red or processed meats can increase your risk.
Weight: leaner people are less likely to develop bowel cancer than obese people.
Exercise: being inactive increases the risk of getting bowel cancer.
Alcohol and smoking: high alcohol intake and smoking may increase your chances of getting bowel cancer.
Family history and inherited conditions: having a close relative with bowel cancer puts you at much greater risk of developing the disease.
The most common forms of inherited colon cancer syndromes are:
- Hereditary nonpolyposis colorectal cancer (HNPCC). HNPCC, also called Lynch syndrome, increases the risk of colon cancer and other cancers. People with HNPCC tend to develop colon cancer before age 50.
- Familial adenomatous polyposis (FAP). FAP is a rare disorder that causes you to develop thousands of polyps in the lining of your colon and rectum. People with untreated FAP have a greatly increased risk of developing colon cancer before age 40.
Related bowel conditions: having certain bowel conditions can put you more at risk of getting bowel cancer. Ulcerative colitis and Crohn’s disease are two such inflammatory bowel conditions which may later on lead to development of cancer of the bowel.
SIGNS AND SYMPTOMS
Early bowel cancer may have no symptoms. Some symptoms of later bowel cancer can also occur in people with less serious medical problems, such as haemorrhoids (piles).
The initial symptoms of bowel cancer include:
- blood in your stools (faeces) or bleeding from your rectum
- a change to your normal bowel habits that persists for more than six weeks, such as diarrhoea, constipation or passing stools more frequently than usual
- abdominal pain
- unexplained weight loss
As bowel cancer progresses, it can sometimes cause bleeding inside the bowel. Eventually, this can lead to your body not having enough red blood cells. This is known as anaemia.
Symptoms of anaemia include:
In some cases, bowel cancer can cause an obstruction in the bowel. Symptoms of a bowel obstruction include:
- abdominal pain
SCREENING FOR COLORECTAL CANCERS
Screening tests are recommended in healthy individuals with no signs of cancer to detect any early changes. Diagnosing early colon cancer provides the greatest chance of a cure. People with an average risk of getting colon cancer should consider screening at 50 years of age. For individuals who are at a greater risk, such as those with hereditary conditions predisposing them to getting colon cancer should consider screening sooner.
If your signs and symptoms meet the criteria for colorectal cancer, you will initially undergo a DRE (digital rectal exam: your doctor will examine your rectum through your anal orifice with the aid of a finger, to look for a lump, texture and color of stool, and to look for blood if present).
If further evaluation is required, patients undergo sigmoidoscopy and colonoscopy for detailed look at the intestines.
Once you’ve been diagnosed with colon cancer, tests are ordered to determine the extent (stage) of your cancer. Staging helps determine what treatments are most appropriate for you.
Staging tests may include imaging procedures such as abdominal and chest CT scans. In many cases, the stage of your cancer may not be determined until after colon cancer surgery.
Treatment of colorectal cancers depends on the extent of the disease. The three primary treatment options are surgery, chemotherapy and radiation.
If the cancer is at a very early stage, it may be possible to remove just a small piece of the lining of the colon wall. This is known as local excision.
If the cancer has begun to spread into the muscles surrounding the colon, it will usually be necessary to remove an entire section of your colon. Removing some of the colon is known as a colectomy.
Sometimes the bowel is re- attached at the time of the first operation, but a stoma is put in place to reduce the risk of complications if the re-attachment does not heal well.
In this case, it will be necessary to find a way of removing waste materials from your body without stools passing through your anus. This is done using stoma surgery. Stoma surgery involves the surgeon making a small hole in your abdomen, which is known as a stoma. There are two ways that stoma surgery can be carried out.
An ileostomy is where a stoma is made in the right-hand side of your abdomen. Your small intestine is separated from your colon and connected to the stoma, and the rest of the colon is sealed. You will need to wear a pouch that is connected to the stoma to collect waste material.
A colostomy is where a stoma is made in your lower abdomen and a section of the colon is removed and connected to the stoma. As with an ileostomy, you will need to wear a pouch to collect waste material.
In most cases, the stoma will be temporary and can be removed once your colon has recovered from the effects of the surgery.
Radiotherapy and chemotherapy can be given either before the surgery to shrink the tumor, or after the surgery to get rid of any redual tumor left. Chemotherapy may also be given in case of incurable colon cancer, to reduce the symptoms and improve quality of life. This is called palliative treatment.
Newer anti-cancer treatment is now available too, referred to as biological treatment. These include the drugs cetuximab, bevacizumab and panitumumab, which are usually used in combination with chemotherapy and radiotherapy.
These treatments are not available to everyone with bowel cancer. The National Institute for Health and Clinical Excellence (NICE) in the UK has determined that specific criteria need to be met before they can be prescribed.
PREVENTING BOWEL CANCER
There are several ways to reduce your risk of developing bowel cancer.
Research suggests that a low-fat, high-fibre diet that includes plenty of fresh fruit and vegetables (at least five portions a day) and wholegrains can help reduce your risk of getting bowel cancer. It can also reduce your risk of other types of cancer and heart disease.
It is recommended that you do not eat a lot of processed meat and red meat. The Department of Health advises people who eat more than 90 grams (cooked weight) of red and processed meat a day to cut down to 70 grams.
There is a strong body of evidence to suggest that regular exercise can lower the risk of developing bowel cancer, as well as other types of cancer.
It is recommended that adults should do at least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity (i.e. cycling or fast walking) every week..
Try to maintain a healthy weight. Changes to your diet and an increase in your physical activities will help to keep your weight under control.
If you smoke, giving up will reduce your risk of developing bowel cancer, as well as many other types of cancer.