Colon Cancer Overview
The cancer of the colon and the rectum – the end of the large intestine – is called colorectal cancer or more commonly colon cancer. It is the third most common cancer in men and fourth most common cancer in women in the US.
What is Colon Cancer?
In our digestive system the small and the large intestine play a major role in digesting food and removing waste material. The large intestine has 4 colon sections and the rectum from where the waste of the body is sent out. These sections of the intestines have very thick walls with several layers of tissues.
The cancer begins as a polyp (an abnormal growth of tissue) in the innermost layer of the colon or the rectum. However, it may take several years before you know they exist, and by that time they likely already would have become cancerous. From the innermost layer the cancer starts spreading to the outer layers. Indeed, the doctor analyses the progression of cancer by analyzing the extent of the growth to different layers. If it has only penetrated the innermost layer, it is colon cancer in its first stage. Almost 90% of colon cancers are caught at the innermost layer. Other types of tumors such as lymphoma, carcinoid tumors – which develop inside the actual colon or rectum – are rare.
According to the American Cancer Society there will be over 100,000 new cases of colon cancer. and more than 40,000 new cases of rectal cancer in the United States this year. The good news is that the number of deaths resulting from colon cancer has significantly decreased over the past decade or so, as new medical techniques like colonoscopy have enabled the cancer and the polyps to be detected earlier and removed completely.
Causes and Risk Factors
The causal factors of colon cancer have not yet been precisely pinpointed, although doctors and researchers have noted certain factors that may increase the risk of the disease. These include:
- Colon Polyps: Under normal circumstances, chromosomes control the growth of the cells in our body. But if these chromosomes are damaged then the cells may start growing abnormally and develop into polyps. Over time, these colon polyps may acquire additional damaged chromosomes, which can lead to cancer. Doctors believe this is the most common cause of colon cancer.
- Diet: A diet high in fats may result in colon cancer. This is because some of the breakdown products of fat may lead to the formation of cancer causing chemicals or carcinogens. It has been found out that countries where fat consumption is high have higher rates cancer patients than those countries where fiber intake is high and fat intake is low.
- Age: A person above the age of 50 is more at risk of getting colorectal cancer than a younger man or woman.
- Family history: About 20% of all colon cancer patients are linked to a family history of the disease. However, this is not considered to be a major factor in acquiring colon cancer (some 80% of patients do not have colon cancer in their families).
- Prior case of cancer: If you’ve ever had colon cancer before – and even if it was completely removed – you have a significantly higher chance of developing a new cancer in other areas of the colon or rectum. Some reports have also shown that a person suffering from testicular cancer may be more prone to having colon cancer.
- Bowel diseases: A disease of the bowel such as ulcerative colitis and crohn’s disease, cause inflammation of the colon over a long period of time. Some ulcers may be present on the lining and cancer may develop.
- Smoking: Apart from smoking being associated with lung cancer, it has also been shown that smokers have a 30-40% greater risk of getting colon cancer than non-smokers.
Colon Cancer Symptoms
The following symptoms may be indicative colon cancer, although in its initial stages signs are generally not very apparent.
- Diarrhea, constipation etc. bowel problems that do not get better
- Blood in the urine
- Abdominal pain
- Weight loss with no known reason.
- Thin stool
However, even if you are experiencing all of the above-mentioned symptoms, that does not necessarily mean you have colon cancer. Although you should certainly inform your doctor about it and let the definitive tests be performed.
Tests and Detection
As colon cancer occurs internally, a physical examination alone is not effective in detecting the disease, however there are a variety of screening methods available
Colonoscopy is by far the best way to detect colon cancer. This method allows the doctor to see the entire colon and detect the presence of polyps or cancerous tissues. Polyps can even be removed at this stage, though a tissue sample may be taken for further analysis to check for the presence of cancerous tissues.
In fact, virtual colonoscopy has also become a means of detection. With this method, air is pumped into the colon and a CT scan is done. This provides the doctor with an enlarged X-ray of the colon and the image is better than with a normal colonoscopy.
Sometimes the doctor may also perform a sigmoidoscopy, where a tube is inserted through the rectum to check for polyps or tumors. But as the complete colon cannot be seen, a colonoscopy is still a better choice.
A barium enema X-ray is a method in which you are given a white chalky liquid containing barium. This marks the outline of the intestine when an X-ray is taken and any tumors are detected as black spots.
Another method is a stool blood test or a fecal occult blood test to find small amounts of blood that may remain hidden in the stool. This provides a rough idea of the possibility of cancer and if the test is positive you may need to undergo a colonoscopy for further confirmation. However, this is not a very reliable testing method as many cancer patients will have negative tests.
Depending on the stage of the cancer and the extent to which it has spread, treatment methods may vary. In the initial stages the doctor may use colonoscopy to remove the damaged part of the colon.
More extensive surgery is required for the stage I, II or III cancer. The abdomen is cut and the cancerous tissue on the colon along with a few inches of healthy colon on either side is removed and the rest sewn together. The colon cancer surgery may also be performed using laparoscopy, where a small incision on the lower abdomen allows a tube to be passed inside the body so the cancer can be removed. This method is less invasive and the recovery is faster.
When the cancer has attached to an internal organ like the liver, or the inner lining of the abdomen, radiation therapy may be used to remove the abnormal growth. This method also allows the cancer to be removed from parts not easily visible and where surgical removal is difficult. Radiation can be given externally or internally.
Chemotherapy combined with medication is another possible solution for people suffering from stage III or IV cancer. The survival rate of patients who have undergone chemotherapy is quite high. In this method a drug is given to the body intravenously or orally. This spreads throughout the body killing the cancerous cells and reaching all the distant organs. However, the danger with this method is the side effects, as normal healthy cells can also be affected.
In general, men and women over the age of 50, those individuals who have a history of the disease in the family or who have had cancer before, need to get a colonoscopy done regularly to check for the presence of polyps or growths.
Also, changing to a low fat, high fiber diet is always a good idea to fight against all types of cancers. In particular fiber-rich foods such as fruits, vegetables and whole grains help create bulkier stools that help to rid the body of waste materials and keep the colon clear. Some studies also suggest that taking a daily multivitamin containing folic acid or a calcium supplement can lower colorectal cancer risk.
Aspirin has been also found to prevent the growth of polyps but this may have side affects and it is not recommended to take the medication without consultation with your doctor.
You can also have a blood test done to test for a family history of colon cancer.