Colorectal cancers are a common type of gastrointestinal cancer caused by any abnormal growth in the colon or the rectum. Colon and rectal cancers have several common features and hence they are grouped together as colorectal cancer.
Globally, colorectal cancer is the third most common cancer in men and the second most common cancer in women. In 2018, more than 1.8 million new colorectal cancers were diagnosed among men and women of all ages.
The incidence of colorectal cancer in India is lower than that in Western countries. Colorectal cancers are the seventh most common type of cancer in India.
What is colorectal cancer?
Colorectal cancer occurs when the cells lining the colon or the rectum begin to grow and divide abnormally, resulting in a mass of tissue, known as a polyp. All polyps are not cancerous, but the ones that continue to grow may become cancerous.
The exact reason behind this abnormal growth and division is unknown, but researchers believe that these factors may play a role:
- family history
- high intake of red meat
- alcohol intake
- certain medical conditions
The most common symptoms associated with colorectal cancer are:
- blood in stools
- loose stools or constipation
- abdominal pain or cramps
- incomplete bowel emptying
- unintentional weight loss
These symptoms overlap with several gastrointestinal medical conditions and hence, in most cases colorectal cancer is diagnosed in the advanced stages.
Diagnosing and managing colorectal cancer during the early stage is the best way to improve the treatment outcomes and the quality of life. Detection of colorectal cancer at an early stage can be achieved through regular screening for these cancers.
Screening Guidelines for colorectal cancer
According to the American Cancer Society, people with an average risk of colorectal cancer should begin screening at the age of 45 years. Screening for colorectal cancer can be done either with a stool-based test or through a visual examination.
People who have good health and life expectancy can continue screening till the age of 75 years. If people between the age of 76 to 85 years want to continue screening, they must consult a doctor to make the best decision.
However, an individual over the age of 85 years is not eligible for screening. An average risk individual does not have a personal or family history of colorectal cancer, personal history of inflammatory bowel disease like Crohn’s or ulcerative colitis.
Types of screening methods for colorectal cancer
The following tests are recommended to screen for colorectal cancer:
These are non-invasive tests in which a sample of stool is collected and examined in the laboratory to look for signs of colorectal cancer, such as blood in stools.
Stool tests are further divided into the following types:
- Faecal immunochemical test (FIT) or Immunochemical faecal occult blood test (iFOBT): In this test, the presence of occult (hidden) blood in the stools is tested. Blood in stools may indicate polyps or cancer. This test should be done annually.
- Guaiac-based faecal occult blood test (gFOBT): In this test, the stool sample is tested on a special card coated with guaiac (a plant-derived substance). If there is blood in the stool sample, then the card changes its colour. This test should be done annually.
- Stool DNA test: This test identifies DNA changes in the cells of a stool sample and looks for abnormal DNA associated with colon cancer or polyps. The test also detects hidden blood in the stool, which can indicate the presence of cancer. This test should be done every 3 years.
Direct visualisation screening:
Direct visualisation screening can be done with the following test:
- Colonoscopy: In this test, the doctor looks at the entire length of the colon and rectum with a colonoscope, which is a flexible tube with a light and small video camera on the end. Special instruments can be passed through the colonoscope to take a biopsy sample or to remove any suspicious-looking areas such as polyps, if needed. Colonoscopy is done every 10 years for individuals at average risk for colorectal cancer.
Choosing a test
If a person wants to undergo a screening test for colorectal cancer, they should consult their doctor to know which screening test would be the best option for them.
The test characteristics, its benefits, harms, and costs should be considered before choosing the test. Additionally, the pros and cons of each test, patient preference, comorbid conditions, and test availability is also considered.
Prevention of Colorectal Cancer
There is no particular way to prevent colorectal cancer. But, following the below-given measures may help in reducing its risks:
- Avoid eating red meat. According to studies, eating red meat increases the risk of colorectal cancer by 22%.
- Limit or quit the consumption of alcohol. Consumption of alcohol increases the risk of colorectal cancer by 8%.
- Quit smoking. Smokers have a 114% higher risk of adenomatous polyps and colorectal cancer.
- Lose weight if you are overweight. Having a high body mass index increases the risk of colon cancer.
- Exercise regularly. Staying active reduces the risk of colon cancer by 20% and rectal cancer by 13%.
- High fibre diet helps reduce risk of colon/rectum cancer. Use of high fibre content foods and salads in daily diet can help increase fibre content in daily diet.
- According to studies, the use of aspirin reduces the risk of colorectal cancer by 40%. However, its use is not recommended in the average-risk population due to the risk of GI bleeding and haemorrhagic stroke.
- Calcium supplements may reduce the risk of adenomatous polyps by 26% and colorectal cancer by 22% but such supplements should be taken with medical advise.
- Statins may reduce the risk of colorectal cancer by 50%.
Any medication needs to be taken in consultation with your doctor.
You can read more about colon cancer here.