The large intestine in the human body comprises of the caecum (a blind-ending pouch to which the appendix is attached), the Colon and rectum. The Colon is further divided into the ascending, descending, transverse and sigmoid colon depending upon its anatomical location. The abnormal or cancerous growth of any of these parts is referred to as colon cancer. The last several inches of the large intestine comprised the rectum and grouped together colorectal cancers are one of the most common cancers prevalent in the world.
Many times, colon cancer begins as benign, small (non-cancerous) outgrowths on the surface of the colon which are referred to as adenomatous polyps. These initially non-cancerous outgrowths can proceed towards cancers if left untreated for long periods of time.
Polyps are believed to rarely produce symptoms and hence are very hard to detect in their earlier stages. Therefore, doctors often tend to recommend regular screening tests to detect polyps and help halt their progression to colon cancer. It is especially done for patients with a strong family history of colon cancers and is started from an early age.
2. Causes and Risk Factors
Most parts of our body continue to undergo constant wear and tear. It is a normal phenomenon in which old cells die, and new ones are formed to take their place, however sometimes because of a small alteration in the normal cell genetics an abnormal cell is produced which does not carry the standard mechanism of cell death within itself. This cell then continues to divide in a haphazard manner and may over the years proceed to areas of cancerous growth. A similar process may happen in the colon and rectum and may be the prequel to colorectal cancers.
As mentioned earlier, colon cancer often begins as small non-cancerous outgrowths on the surface lining the inside of the colon. These are called polyps and are often found in clusters. Usually, they take the shape of mushrooms and can be present in large numbers. Sometimes, these precancerous lesions do not outgrow from the surface and are hence flattened areas of abnormal growth. These are called nonpolypoid lesions which also carry the risk of mutating into cancers over the years.
Mutations (abnormalities) in some inherited genes have been linked to the development of colon cancers in individuals. These can be passed for future generations which then have an increased likelihood of developing colon cancer. It is not necessary that every individual carrying the gene mutation will develop colon cancer at some point in their lives; however, the risk of cancer development is certainly increased in such individuals.
There are two identified inherited syndromes of cancer that tend to run in families. FAP or Familial Adenomatous Polyposis is a rare genetic disorder that causes the development of innumerable polyps to line the surface of the colon and rectum. It greatly increases the individual’s risk of colon cancer development, even before the fourth decade of life.
HNPCC or Hereditary Non-polyposis Colorectal Cancer is another inherited disorder that increases an individual’s risk of development of colon cancer and also other cancers as well. This is sometimes referred to as the Lynch Syndrome and also increases the risk of cancer development before the age of 50. Individuals with family histories of these two syndromes are frequently advised by their doctors to undergo screening programs from an early age to prevent the development of colon cancer.
Although individuals with the aforementioned inherited disorders may tend to develop cancers at an early age, colon cancer is independently also risked to increasing age. Most of the un-inherited cancers tend to occur at the age of 50 and the risk increases with age.
Colon cancer is believed to be more prevalent amongst the African American race. However, people in other parts of the world are also at risk.
If a patient has suffered from colorectal polyps or colon cancer in the past, their chances of developing cancer and recurrence of cancer are more compared to the rest.
Inflammatory Conditions Affecting the Colon:
There are some chronic diseases of the colon that are believed to increase the individual’s risk of developing colon cancer. Inflammatory conditions like Crohn’s and Ulcerative colitis are identified as two such conditions. People diagnosed with these conditions should follow up regularly with their doctors and discuss possible treatment and prevention plans within time to prevent colon cancer development.
Family History of Colon Cancer or Polyps:
Individuals with a parent, sibling or children with cancers of the colon or adenomatous polyps have an increased propensity of developing colon cancers. It may be due to inherited genes mutations in the family or possibly due to exposure to a similar carcinogen within a family. Patients with strong family histories are repeatedly advised to undergo regular screening programs from an early age. It may in time prevent the development of cancer and save the individual from a lot of distress.
There are many credible studies that have associated the risk of developing colon cancer to some dietary factors. Some studies have linked the association of colon cancer to an increased consumption of red meat, whereas others believe colon cancer to be also associated with a diet low in fiber and high in fat. Research in this area is still underway to create promising links between diet and the risk of developing colon cancer.
Exercise and Lifestyle:
The risk of developing colon cancer has been proved to be directly related to a sedentary lifestyle and also to obesity. Many research studies have shown a possible link between exercise and lowering the risk of colon cancer development.
Researchers believe that long-standing diabetes and insulin resistance increases an individual’s chances of developing colon cancer.
Smoking and Alcohol:
Smoking and alcohol are independently thought to increase the risk of colon cancer development significantly. Both these substances are linked to some different cancers, and many multicenter large-scale studies have proven the association.
Like chemotherapy, radiation therapy is believed to be an effective cure for cancer sometimes in combination with surgery and at other times with chemotherapy. However, it tends to carry its side effects. It is now believed that radiation therapy given to the abdomen (for any reason) can adversely affect the colon and increase the risk of development of colon cancer.