Colon cancer is cancer in the lowest part of the digestive system, the large intestine or colon. Cancer occurs when cells in the body grow abnormally out of control. Most colon cancers occur when small, noncancerous (benign) clumps of cells called adenomatous polyps on the inner walls of the large intestine change and transform into cancerous (malignant) tumours over time. Identification of these benign polyps before they become cancerous is therefore especially important and can be done by regular screening tests.
Colon cancer cells lead to many complications by invading and damaging healthy tissues in the vicinity. Also, once malignant tumours form, the cancer cells may travel through the blood and lymph systems, eventually spreading to other parts of the body.
Signs and symptoms
Symptoms of colon cancer depend on the size and location of the cancer. There may be no obvious symptoms in the initial stages of the disease. However, symptoms increase in quantity and degree of severity as the disease progresses.
Colon cancer manifests itself in two forms, local (confined to the colon) and systemic colon cancer (cancer has spread to different parts of the body). There is a variation in the signs and symptoms of these two forms.
Local colon cancer symptoms
These symptoms include a change in bowel habits that include constipation or diarrhoea, feeling of incomplete bowel evacuation, blood (either bright red or very dark) in stools, “pencil stools” (stools thinner than normal) and persistent abdominal discomfort accompanied by cramps, gas or pain. Consult your doctor right away if you are experiencing similar symptoms over a few days.
Systemic cancer symptoms
Characteristic symptoms of systemic cancer include unexplained weight loss, loss of appetite accompanied by fatigue or weakness, nausea, anaemia and jaundice. If you experience any of these symptoms, you should be seen by your health care provider at the earliest.
Regular colon cancer screenings can detect colon cancer early and potentially save your life. Early detection is advisable as polyps or growths on the lining of the intestine can be found early and removed before they develop into cancer. Colon cancer screening is dreaded by many people as they think it might hurt or they find it embarrassing. It is important to understand your doctor performs these procedures on a regular basis and there is no need to feel embarrassed. Also, you will be kept comfortable during the procedure with anaesthesia and not feel pain.
If your symptoms resemble colon cancer, your doctor will review your medical history and order blood tests. The following procedures may be recommended:
- Colonoscopy- A long and flexible slender tube is attached to a video camera and monitor, and the entire colon is captured on a screen. This helps to detect suspicious areas from where biopsies (tissue samples) can be taken for analysis using surgical tools passed through the tube.
- Virtual colonoscopy/CT colonography- Multiple CT scan images are combined to create a detailed picture of the inside of your colon. This is usually recommended for people who are unable to undergo colonoscopy.
Your doctor might recommend treatment options taking into account factors such as the stage of cancer (whether it is in the initial or the final stages) and the overall health of the patient. The different treatment options include surgery, chemotherapy and radiation.
- Surgery for early or initial stage cancer: Your doctor may employ colonoscopy for removing small localised polyps. A procedure called endoscopic mucosal resection may be used for larger polyps. If colonoscopy does not yield the desired result, laparoscopic surgery may be used.
- Surgery for invasive colon cancer: A procedure called partial colectomyis used if the cancer has moved into or through your colon. This involves removing the cancer containing part of the colon, along with a portion of normal tissue on either side.
- Surgery for advanced cancer: If the cancer has reached a point of “no cure”, or your general health conditions have dropped considerably, then surgery isn’t done to cure cancer; it is done to bring relief from symptoms such as bleeding and pain.
Chemotherapy involves using drugs to destroy cancer cells. It is usually taken up after surgery to relieve the symptoms of cancer that has spread to either lymph nodes or other areas of the body. It can also be used to shrink the cancer before the surgery.
Radiation therapy uses high energy radiation such as X-rays to kill cancerous cells. It is usually employed in later stages of cancer and together with chemotherapy it can reduce the risk of cancer recurrence in specific areas.