Colon Cancer

Q 1 what is colon cancer? 

Colon cancer is a type of cancer that begins in the large intestine (colon).  Food travels through the small intestine to the colon. The waste matter that’s left after going through the colon goes into the rectum and stored there until it passes out of the body through the anus.  Colon cancer typically affects older adults, though it can happen at any age.   

 Q 2 What are the types of colon cancer?

  • Adenocarcinomas make up about 96% of colorectal cancers
  • Carcinoid tumors
  • Gastrointestinal stromal tumors (GISTs)
  • Lymphomas
  • Sarcomas

Q 3 what causes colon cancer? 

  • Family history

Having a family history of bowel cancer in a first-degree relative – a mother, father, brother, or sister – under the age of 50 can increase your lifetime risk of developing colon cancer. Common hereditary syndrome includes familial adenomatous polyposis, Lynch syndrome or HNPCC, hereditary breast, and ovarian cancer syndrome. 

  • Digestive disorders: Inflammatory bowel disease such as ulcerative colitis and Crohn disease, risk of colon cancer begins approximately 8 to 10 years after the initial diagnosis 
  • Obesity 
  • Diabetes
  • Tobacco use
  • Excess consumption of alcohol
  • Diet high in red and processed meat 
  • Lack of physical activity


Screening is used to look for cancer before you have any symptoms or signs

  • For average-risk individual: Start screening at the age of 50 and continue till 75. 

Any of the below methods can be used 

  • Flexible sigmoidoscopy, every 5 years or every 10 years with FIT or FOBT every year
  • Colonoscopy, every 10 years
  • Guaiac-based FOBT, every year
  • FIT, every year
  • For high-risk individual: Start screening at an early age with colonoscopy or with sigmoidoscopy. 

 High risk includes who have 

  • A family history of the disease
  • An inherited syndrome such as Lynch syndrome, FAP
  • Inflammatory bowel disease 
  • Have been diagnosed with colorectal cancer in the past.

Consultation with a doctor and genetic counselor are strongly suggested

Q 4 What are the symptoms of colon cancer? 

  • A persistent change in bowel habit: maybe increasing constipation or alternating bouts of constipation and diarrhea.
  • Bright red or very dark blood in the stool
  • Pain, or vague discomfort in your abdomen
  • Weakness and loss of weight 
  • Abdomen fullness and vomiting 
  • Unexplained iron-deficiency anemia

A word of caution 

All of these symptoms can also be caused by conditions that are not cancer. Kindly consult your doctor first. 

Q 5 How colon cancer is diagnosed? 

  • The doctor will perform a general physical examination and digital rectal examination (DRE) in which the surgeon will insert a lubricated, gloved finger in anus to feel for signs of disease. 
  • Flexible sigmoidoscopy or colonoscopy to look for cancer in the entire rectum and colon.  A flexible, lighted tube called a colonoscope is inserted into the rectum and the entire colon to look for polyps or cancer. 
  • During a colonoscopy, a biopsy is done from colon mass to confirm the diagnosis and to know the type of cancer. 
  • Biopsy means removing a small piece of tissue from cancer mass and sent it to a pathologist for examination under a microscope. 

A word of caution 

  • There is a common myth that taking biopsy leads to the spread of cancer cells in the body. This is not true. Taking biopsy does not lead to the spread of cancer cells in the body.
  • Biopsy confirms that it is cancer and not infection and also helps in knowing the type of cancer so that further treatment can be planned accordingly.  

Further testing

Once the colon cancer has been diagnosed, further tests are done to look for a local extension of disease and to confirm whether cancer cells have spread to other parts of the body or not. These tests may include:

  • Blood tests – to assess the state of liver, kidneys and bone marrow
  • Blood tumor marker carcinoembryonic antigen ( CEA ) 
  • CT/MRI scan – To find out the local spread of disease 
  • Chest X-ray – To check if cancer has spread to the lungs or not 
  • Sometimes a PET scan – To know the distant spread of disease 

Q 6 What is colon cancer staging? 

Staging is a measurement of how far cancer has spread.

After all the tests have been completed and the results are known, it should be possible to predict what stage the cancer is. The higher the stage, further cancer has spread

The 4 main stages are:

  • Stage 1 – the cancer is still contained within the lining of the bowel 
  • Stage 2 – cancer has spread beyond the layer of muscle surrounding the bowel and may have entered the surface covering the bowel or nearby organs
  • Stage 3 – cancer has spread into nearby lymph nodes
  • Stage 4 – cancer has spread beyond the bowel into another part of the body, such as the liver

A word of caution 

The above staging is a simplified version for your basic understanding. The reader is advised to follow the TNM staging system developed by the American Joint Committee on Cancer (AJCC) in which 

  • T stands for the size and location of primary cancer
  • N stands for nodes. It tells whether cancer has spread to the nearby lymph nodes
  • M stands for metastasis. It tells whether cancer has spread to distant parts of the body

Q 7 How colon cancer is treated? 

When deciding treatment options for a particular patient, the doctor will consider the following factors and will decide individual treatment plan:

  • The size of the cancer
  • The stage of the cancer
  • The location of the cancer
  • Your overall health and ability to recover from surgery, radiation therapy or chemotherapy
  • How a treatment will affect bowel movements 
  • Your personal preferences

Following are the general guidelines but treatment may vary from patient to patient:  

Two main categories for treatment purpose are

  • Early-stage colon cancer: Surgery followed by chemotherapy
  • Advanced colon cancer (metastatic):  Option include chemotherapy / targeted therapy / immunotherapy. Treatment decision depends upon organ involved, the general condition of the patient, and mutation testing of cancer.

Surgery: Colectomy

Colectomy (partial or total) is the removal of a portion of the colon containing cancer and surrounding lymph nodes. 

After removal of the diseased segment, two ends of the bowel stitched together. The surgeon may create a stoma depending on the condition of the bowel during the operation. The stoma can be permanent or temporary depending on the extent of resection. The temporary stoma can be reversed after the completion of chemotherapy. 

  • Hyperthermic Intraperitoneal Chemotherapy (HIPEC)  

It is used in advanced cases of colon cancer especially when cancer has spread to the inner lining surfaces of the peritoneal (abdominal) cavity.

The surgeon will remove all visible cancer that can be removed throughout the peritoneal cavity. This is known as cytoreductive surgery. Following cytoreductive surgery, in the operative setting, the surgeon will administer HIPEC treatment. HIPEC means that the solution containing chemotherapy is heated to a temperature greater than normal body temperature and it is delivered into the abdominal cavity. 

Q 8 What is a stoma? 

A stoma is an artificial opening created when the healthy part of your bowel is brought out onto the surface of your abdomen. Your stool will be passed through this opening instead of through your rectum as before. You will need to wear an appliance (bag) to collect your stools.