Colorectal cancer is often addressed as bowel cancer, colon cancer or rectal cancer. Colorectal refers to the colon and the rectum. The name is given based upon the region the cancer starts from. Cancer begins to develop when the cells in the body can not be controlled and rapidly grow. The colon and rectum are part of the large intestine, included in the gastrointestinal system (GI). 

The colon makes up the majority of the large intestine, and it is a 5ft long tube that allows food to travel through. The colon is broken up into 4 parts, and they are named according to how the food would travel through. 

 

1. Ascending colon

• Starts in the cecum 
• Cecum allows undigested food from the small intestine to enter 
• Continues upward on the right side of the belly

2. Transverse colon 

• Goes across the body from the right side to the left side

3. Descending colon 

• It ‘descends’ which means travels downwards from the left side

4. Sigmoid colon 

• It is in an ‘S’ shape
• Joins the colon to the rectum 

The function of the colon is to absorb water and salt from the food that remains after it has passed the small intestine. Any remaining waste after it has passed through the colon will enter the rectum and will be stored there until it passes through the anus. 

Colorectal cancers begin once there is an irregular growth that can be found on the lining of either the colon or rectum, these irregular growths are called polyps. Certain polyps are able to develop into cancer but in other cases, they may not develop into cancer. This is based upon what type of polyps it is. Adenomatous polyps also known as adenomas are the type of polyps that has the chance of eventually changing into cancer. Adenocarcinomas are the most type of colorectal cancer and begin in the mucus that lines the wall of the colon and rectum. It is often harmless at first but as cancer grows, so do the risks. Hyperplastic polyps are one of the most common and are often not pre-cancerous, however, those with larger polyps would require colorectal cancer screening more often. If a polyp is larger than 1cm or there is an abundance of them, it is also a risk factor and increases the individual’s chance of developing colorectal cancer.

If cancer begins to grow in the polyp, undetected it can eventually start to grow into the wall of the colon or rectum, starting from the innermost layer and growing outwards. It becomes a danger when cancer begins to grow outward because then it has the possibility of growing into the blood vessels and can eventually travel to other regions of the body. The stages are assigned based upon how the cancer is growing in the wall and the stages progress if the cancer has begun to spread. 

Treatments for colorectal cancer include surgery, chemotherapy, radiation therapy or targeted therapy. A bowel resection is the primary surgery treatment that is performed by removing a portion of the intestine depending on where the cancer is. Chemotherapy in certain cases is also used through drug treatments either given individually or combined with other treatments. Radiation therapy is primarily used for cancer that can begin in the rectum and can be associated with chemotherapy through chemoradiation. Targeted therapy is intended for advanced stages of colorectal cancer, and often is combined with chemotherapy to tackle the cancer. Follow up care after any form of treatment is essential to ensure the treatment is working. Frequent screening is recommended to those who have polyps, this can allow early detection if cancer begins to grow.