What is Colorectal Cancer?
Colorectal Cancer (also known as bowel cancer and colon cancer) is cancer found in the colon or rectum (part of large intestines).
Image source: OncoLink
Most colon cancer start as a growth on the inner lining of the colon called polyps. Over time, these polyps can change into cancer.
Image source: National Cancer Institute
Factors which can increase chance of cancer include:
i) If polyp is larger then 1cm
ii) If more than 2 polyps are found
iii) If the cells in the polyp show pre-cancerous changes called dysplasia
How does the colon look like?
Image source: Mayo Clinic
The colon is around 5 feet long for undigested food to pass through before coming out as waste. The first section is called ascending colon, second section is the transverse colon and the third section is the descending colon. The last 2 sections are the sigmoid and rectum where the waste products sits and wait before being excreted. If you are constipated, the waste sits here longer.
How does Colon Cancer spread?
Over time a polyp can grow into the wall o the colon deeper into the layers of the wall and finally into blood vessels or lymph nodes. The final 4th stage is when the cancer has spread to other parts of the body. The chance of surviving the cancer gets LESS with each increasing stage.
Image source: My Support 360
What are the risk factors?
1) Age (most colon cancers start after 50 years old)
- Long term consumption of read meat or processed meat
- High temperature cooking such as barbecuing and pan-frying
- Low fibre intake (constipation increases time toxins in contact with the colon)
- Smoking increases the risk of colon cancer and chance of dying from colon cancer
4) Family history
- The increase in life time risk related to family history ranges from two to six fold
- Risks are greatest in relatives of patients diagnosed young, tow or more affected relatives or relatives of patients with colon cancers
- Being overweight, having high fat diet and physical inactivity increases the risk of colon cancer
Why screen for colon cancer?
It is important to undergo screening for colon cancer because detecting colon cancer EARLY increases the chances of survival. Late stage cancers (such as stage 3 or 4) have worse prognosis. In fact at the polyp stage, the removal of polyp eliminates the chance of it progressing to later stage of cancer.
For those who have had polyps in the past should arrange for one or two yearly screening/surveillance. The screening of colon is by using a flexible endoscope called colonoscopy.
Screening is the testing of asymptomatic individuals to determine the risk of developing colon cancer and surveillance is the ongoing monitoring of individuals who have an increased risk for the development of the disease.
In conclusion, colon cancer is a major public health concern and is the 2nd most common cancer in Malaysia.
Cancer statistics in Malaysia:
Screening lowers the incidence and mortality of colon cancer and colon cancer is preventable through removal of premalignant polyps and is curable if detected and treated early.
References: Johns LE et al. Am j Gastroenterol. 2001;96(10):2992, Morb mortal Rep 2011;60(26):884, Globocan 2012
Dr. S. Mahendra Raj
Gastroenterologist (gut physician)