What is colorectal cancer?
Colorectal cancer is the cancer of the colon and rectum. It is also known as bowel cancer or cancer of the large intestine.
Colorectal cancer is the most common cancer in Singapore and the second most common cause of death after heart disease.
Colorectal cancer usually begins as polyps that develop as a result of errors in the way cell grow and repair in the lining of the colon or rectum. Majority of polyps are benign but some have the potential to become cancerous.
Removing the polyps early can prevent colorectal cancer.
What causes colorectal cancer?
Nobody knows exactly why a cell become cancerous but it is thought that the genes in the cells are damaged or altered and they trigger the cells to become abnormal and grow uncontrollably.
Certain risk factors increase your chance of developing colorectal cancer.
- Non-modifiable risk factors
- Ageing -Risk of developing cancer increase as you grow older than 50 years of age
- Family history of colorectal cancer
- Personal history of inflammatory bowel disease
There are some factors that can help to reduce the risk of developing colorectal cancer.
These protective risk factors include:
- Diet – High in fibres, vegetables, fruits, calcium, garlic and low in red, processed meat, animal fat and sugar
- Lifestyle – Plenty of exercise, stop smoking, cut down on alcohol, prevent obesity
What are the symptoms of colorectal cancer?
- Passing of blood in stools, dark stools
- Change in bowel habits: diarrhoea, constipation, narrowing or thinning of stool
- Feeling that bowel does not empty completely
- Abdominal discomfort such as pain or cramps, bloating or fullness
- Weakness or fatigue
- Unintentional weight loss
- Unexplained anaemia
How is colorectal cancer diagnosed?
Once your doctor suspects you may have colorectal cancer, he will order one or more of the following tests:
- Colonoscopy – A colonoscopy is a test where a thin, long and flexible telescope (colonoscope) is inserted through the anus into the rectum and colon. This allows your doctor to visualise the surface of the large intestine looking out for polyps or any suspicious lesions. This is currently the gold standard amongst all the investigations.
- CT colonoscopy – This test uses xrays and special computer software to create images of the colon and rectum.
- Barium enema – This test uses barium, a radio-opaque fluid, to coat the lining of the colon and the outlines are shown on x-rays.
Once the test reveals possible cancer, the next step is to obtain tissue samples (during colonoscopy) and sent to pathologist who will examine them under a microscope. Once confirmed of cancer, the next step is to stage the disease, usually using CT scan and blood tests, to determine the extent of the spread of the disease and also the prognosis. Staging also allows your doctor to decide which treatment option is best for you.
How is colorectal cancer treated?
Treatment options include surgery, chemotherapy or radiotherapy. The type of treatment for each patient will depend on the stage of the disease and the general health.
Surgery. Surgery is the foundation of curative therapy. It involves the removal of the cancer and the adjacent healthy colon or rectum and the surrounding lymph nodes. In the early stage of the disease, surgery can achieve cure in most patients. With advancement in technology, we are now able to perform ‘key-hole’ (laparoscopic or minimally-invasive) surgery in suitable cases instead of open surgery. The advantages are less postoperative pain, early recovery and mobilisation, shorter hospitalisation and earlier return to work and normal activities.
In advanced cases where cure is not attainable, surgery can also help in improving the quality of life for the patient.
Chemotherapy and radiotherapy
Depending on the stage of the disease, one or a combination of the abovementioned treatment may be needed. Chemotherapy is the use of anti-cancer drugs to kill cancer cells and stopped them multiplying whereas as radiotherapy uses high energy radiation beam to achieve similar effects.
Sometimes chemotherapy or radiotherapy may also be required after surgery. This is also known as adjuvant therapy. The purpose is to kill cancer cells that may have escaped from the primary tumour. Occassionally, chemotherapy or radiotherapy may also be given before surgery to shrink the cancer so that it is easier for the surgeon to remove the cancer and achieve a better outcome.
Screening for colorectal cancer
Screening for colorectal cancer, using colonoscopy, can detect early stage cancer and achieve better chance of a cure following successful treatment. In some cases, screening may prevent colorectal cancer by removing polyps or suspicious growths before they turn cancerous.