Colorectal Cancer

Colorectal cancer, also known as bowel cancer, can affect any part of the large bowel (colon) and rectum.

Most colorectal cancers develop on the inner wall of the colon and rectum and usually start with growths called polyps.

These polyps are benign growths and usually harmless, however they can become cancerous if left undetected.

Colorectal cancer may also be called colon cancer or rectal cancer, depending on where the cancer is located and the area it originates from.

Colorectal cancer is the most common cancer in men and second most common in women in Singapore and is more common in people over the age of 50.

One third of colorectal cancer cases are caused by genetics and family history.¹

The three common inherited disorders which have been linked to colorectal cancer are:

• Hereditary Non-Polyposis Colorectal Cancer (HNPCC) (known as Lynch Syndrome) – results in mutations to the genes that protect cells from growing abnormally and turning into cancerous cells.¹
• MYH – Associated Polyposis (MAP) – caused by a genetic mutation in the gene MYH gene which results in numerous (10-100) polyps (abnormal tissue growth) which can become cancerous.¹
• Familial adenomatous polyposis (FAP) – causes significant numbers (100 – 1000) of adenomatous polyps (gland-like tissue growths) in the lining of the large intestine.¹

The TNM system is used to stage colorectal cancer, which helps doctors understand what your cancer looks like. The TNM stands for:

• Tumour – the degree to which the tumour has affected other tissue, for example has it grown outside the wall of the rectum or colon? ⁴
• Node – is a measure of whether lymph nodes have been affected.
• Metastasis – the degree to which the cancer has spread to other organs of the body.

There are five stages (0 – IV) of colorectal cancer, which are explained below:

• Stage 0 (also called carcinoma in situ) – is where abnormal cells are found in the first layer (mucosa) of the wall of the bowel. These abnormal cells have the ability to become cancerous, grow and spread. ⁴
• Stage I – cancer cells have been found in the mucosa, have spread to the next layer in the wall of the bowel called the submucosa, and possibly even the muscle layer of the bowel wall. However no cancer cells have been found in the lymph nodes or other tissue.⁴
• Stage II – IV– there are three sub-categories in each of the colorectal cancer stages from II – IV, which are known as A, B and C. The sub-categories and stages are dependent on the involvement of lymph nodes, associated tissue, organs and distal sites (sites further away in your body from the bowel).⁴