types of cancer

Colon Cancer


Colon cancer in India and other developing countries is a common type of cancer, in the recent past, incidence has increased in India. Doctors have concluded that the increasing consumption of fast food, which is low in fibre, may be a key contributing factor. In India, colon and rectal cancers are seen in relatively young patients, as compared to the western population. What is Colon Cancer? Colon cancer is the cancer of large intestine (colon), the lower part of our digestive system. Rectal cancer is cancer of the last 6 inches of the colon. Most cases of colon cancer begin as small, non-cancerous (benign) clumps of cells called ‘adenomatous polyps’. Over time some of these polyps become colon cancers.


As with other cancers, the early symptoms are quite vague. However, the following signs and symptoms are quite common:

  • A change in your bowel habits, including diarrhoea or a change in the consistency of stool for more than a couple of weeks
  • Rectal bleeding or blood in stool
  • Persistent abdominal discomfort, such as cramps, gas or pain
  • Abdominal pain with bowel movement
  • A feeling that the bowel doesn’t empty completely
  • Unexplained weight loss and fatigue
  • Causes

    The causes of colon cancer are often environmental (80%) and sometimes genetic (20%). Since malignant cells have an altered genetic constitution, it implies that in 80% of cases, the environment spontaneously induces change. For those with a genetic predisposition to colon cancer, get the cancer or need less environmental exposure to get the cancer. Carcinogenesis is the process of being exposed to the environment that causes the mutation. Though specific carcinogens (cancer causing agents) have been difficult to identify; some of the causes for Colon Cancer are:

  • Presence of polyps as small, non-cancerous (benign) lumps of cells in the colon
  • A diet rich in fat and starch without fibre
  • Sedentary lifestyle
  • Smoking and alcohol consumption
  • A family history of colon polyps
  • A history of inflammatory bowel disease (two diseases – Ulcerative Colitis and Crohn’s disease)
  • Diagnosis

    In order to determine if a person is suffering from colon cancer, the following screening tests are conducted:

  • A physical examination
  • A blood test called ‘faecal occult’, which identifies hidden blood in the stool
  • This is usually followed by visualization of colon through a procedure known as colonoscopy
  • Other tests including biopsy, where a piece of suspected tissue is taken for examination
  • Treatment

    Once the diagnosis has been confirmed through biopsy, we come to the clinical stage of the cancer. Considering the characteristics of the primary tumour, its penetration depth through the bowel as well as the presence/absence of regional or distant metastases, we arrive at the stage of the cancer. More often than not, the depth of penetration through the bowel or the presence of regional lymph nodes cannot be determined before surgery. There are 4 stages of colon cancer based on the below general criteria:

  • Stage 1: The tumour is confined to the epithelium and has not penetrated through the first layer of muscle in the bowel wall.
  • Stage 2: Here the tumour has penetrated through to the outer wall of the colon or has gone through it, possibly invading other local tissue.
  • Stage 3: Here we can detect any depth or size of tumour associated with regional lymph node.
  • Stage 4: Any of above criteria associated with distant metastasis.
  • The treatment plan is chalked out once the disease is identified and staged. The treatment plan may include options from Medical Oncology, Surgical Oncology and Radiation Oncology depending on the stage of condition and the general health of the patient. Surgical Oncology for Colon Cancer: Surgery is the primary mode of therapy for stages 1 through 3 colon cancer unless there are signs that it won’t allow for complete removal of the tumour. This may happen in advanced stage 3 tumours. However, this is rare and happens in less than 2% of all colon cancer cases. Surgical removal of the affected section of the colon along with its blood supply and regional lymph nodes is called colectomy. Whether a patient requires undergoing a surgery or not depends on multiple factors such as the type, size, location, grade and stage of the tumour, as well as other general health factors such as age, physical fitness and other medical conditions. In many cases, surgery is combined with other cancer treatments such as chemotherapy, radiation therapy Radiation Oncology for Colon Cancer: Radiation therapy for colon cancer is used as a support to surgery if there is a concern about potential for recurrence provided the area of concern will be able to tolerate the radiation dose. Radiation therapy is also used to treat patients with metastatic cancer. It is useful in shrinking metastatic colon cancer to the brain. Radiation therapy is usually completely non-invasive, and does not require a patient to be admitted for the treatment. Medical Oncology for Colon Cancer: Medical Oncology is a modality of treatment in cancer care which uses chemotherapy, immunotherapy and targeted therapy to treat cancer in an effective manner. Medical oncology is usually works in conjunction with surgical oncology or radiation oncology to give the best clinical outcomes. Chemotherapy is beneficial for patients who have had all identifiable tumours removed however could be at risk for recurrence (adjuvant chemotherapy). Chemotherapy could also be used when the colon cancer is in stage 4 and is beyond the scope of regional therapy.

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