Causes of Colorectal Cancer

Medical doctors and researchers are not certain about the main cause of most colorectal cancers, yet there are several risk factors that can increase an individual’s risk of colorectal cancer, but it’s not exactly clear how all these factors might cause colorectal cancer. Generally, colon cancer begins when healthy cells in the colon and rectum develop changes (mutations) in their DNA.

Precancerous Growths: Abnormal cells accumulate in the lining of the colon, forming polyps. These are small, benign growths. Removing these growths through surgery is a common preventive method. Untreated polyps can become cancerous.

Gene Mutations: Sometimes colorectal cancer occurs in family members. This is due to a gene mutation that passes from parent to child. These mutations don’t guarantee that an individual would develop colorectal cancer, but they do increase the chances.

Risk Factors of Colorectal Cancer

Just as explained earlier, there are several factors that increase the risk of colorectal cancer in an individual, and these factors can be divided into two:

1. Unavoidable Factors

Some factors that increase risk of developing colorectal cancer are unavoidable and can’t be changed.

• Age: This risk of colorectal cancer increases as an individual get older, it can be diagnosed at any age, but most individuals with colon cancer are older than 50. For colon cancer, the average age at the time of diagnosis for men is 68 and for women are 72. For rectal cancer, it is age 63 for both men and women.
• Race and Ethnic Background: Jews and Blacks i.e. (African Americans and Africans) are more vulnerable when it comes to colorectal cancer incidence and mortality rates among all racial groups in the world.
• Personal History of Colorectal Cancer of Colorectal Polyps: If an individual had already had colorectal cancer or noncancerous colon polyps, even if it was completely removed; he / she is more likely to develop cancer in other parts of the colon and rectum in the future.
• Family History of Colon Cancer: Individuals who have a family history of colorectal cancer especially from first – degree relatives (i.e. parents, brothers, sisters, grandparents etc.), have a risk of developing colorectal cancer in the nearest future.

The risk further increases if other close relatives have also developed colorectal cancer or if a first-degree relative was diagnosed at a younger age.

• Rare Inherited Conditions: Some gene mutations passed through generations of an individual’s family can increase the risk of colon cancer significantly. Only a small percentage of colon cancers are linked to inherited genes. The most common inherited syndromes that increase colon cancer risk are familial adenomatous polyposis (FAP) and Lynch syndrome, which is also known as hereditary nonpolyposis colorectal cancer (HNPCC).
• Inflammatory Bowel Conditions: Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease can increase the risk of colon cancer.
• Adenomatous Polyps (Adenomas). Polyps are not cancer, but some types of polyps called adenomas can develop into colorectal cancer over time. Polyps removal can prevent colorectal cancer. People who have had adenomas have a greater risk of additional polyps and of colorectal cancer, and they should have follow-up screening tests regularly.

2.   Avoidable Factors

Other risk factors are avoidable. This means an individual can change them to decrease the risk of developing colorectal cancer. Many lifestyle-related factors have been linked to colorectal cancer. In fact, the links between diet, weight, and exercise and colorectal cancer risk are some of the strongest for any type of cancer. Avoidable risk factors include:

• Obesity (Being Overweight): People who are obese have an increased risk of colon cancer and an increased risk of dying of colorectal cancer when compared with people considered normal weight. Being overweight (especially having a larger waistline) raises the risk of colon and rectal cancer in both men and women, but the link seems to be stronger in men.

• Physical Inactivity: People who are inactive (don’t exercise) are more likely to develop colorectal cancer. Involving in regular physical activities may reduce the risk of colorectal cancer.

• Certain Types of Diets: Diets that are high in red meats i.e. beef, pork, lamb and processed meats like hotdogs can raise the risk of colorectal cancer.

• Smoking: People who smoke are more likely to develop and die from colorectal cancer, especially since smoking is known to be the main cause of lung cancer.

• Alcohol: People who tend to drink alcohol moderately or heavily tend to develop colorectal cancer.

• Type 2 Diabetes Patients: Individuals with type 2 diabetes or insulin resistance have an increased risk of colon cancer. Both type 2 diabetes and colorectal cancer share some of the same risk factors (such as being overweight and physical inactivity), yet they have a higher and increased risk.

Prevention of Colorectal Cancer

Certain risk factors for colorectal cancer, such as family history and age, aren’t preventable. However, lifestyle factors that may contribute colorectal cancer are preventable, and may help reduce the overall risk of developing this disease.

• Colorectal Cancer Screening: Getting screened can help to discover colorectal cancer in individuals with no symptoms of the disease. Regularly going for colorectal screening is the best way of preventing colorectal cancer. Doctors recommend that people with an average risk of colon cancer should consider colon cancer screening around age 50. But people with an increased risk, such as those with a family history of colon cancer, should consider screening sooner.
• Aspirin and other Non-steroidal Anti-Inflammatory Drugs (NSAIDs): Some studies suggest that aspirin and other NSAIDs may reduce the development of polyps in people with a history of colorectal cancer or polyps. However, regular use of NSAIDs may cause major side effects, including bleeding of the stomach lining and blood clots leading to stroke or heart attack. 
• Diets and Supplements: Limiting red and processed meats and eating more vegetables and fruits may help lower risk of colorectal cancer. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in colorectal cancer prevention. In recent years, some large studies have suggested that fiber in the diet, especially from whole grains, may lower colorectal cancer risk. Also, people who take calcium and vitamin D supplements have a lower risk of colorectal cancer.
• Alcohol Intake: Excessive alcohol intake has been known to be a risk factor for colorectal cancer; limiting the intake of alcohol can help to reduce the risk of colorectal cancer in any individual.
• Quit Smoking: Long-term smoking is linked to an increased risk of colorectal cancer, as well as many other cancers and health problems. Quitting smoking may help lower the risk of colorectal cancer and many other types of cancer, too.
• Physical Activity: Keeping fit and getting involved in physical activity can help to lower the risk of colorectal cancer and polyps.
• Maintaining a Healthy Weight: It is important for individuals with family history of obesity to maintain a healthy weight i.e. work to maintain their weight. There should be aim to lose weight slowly by increasing the amount of exercise one get and reducing the number of calories one eat.