Causes of Colorectal Cancer
The primary cause of colorectal cancer remains unknown. However, several risk factors that may increase the likelihood of developing this condition will be discussed in detail later. Colorectal cancer is believed to arise from mutations in the DNA of colon or rectal cells, which subsequently impair these cells’ ability to regulate growth and division. As a result, these cells can grow uncontrollably, forming tumors. While many of these abnormal cells are eliminated by the immune system or die off before becoming tumors, some can escape detection and continue to proliferate.
Generally, the development of colorectal cancer begins with the formation of polyps in the intestinal mucosa. Polyps result from the rapid growth and accumulation of cells. Although polyp cells may appear abnormal under microscopic examination, they usually remain localized within the polyps and do not have the ability to spread. Overall, polyps are not categorized as cancers; however, there is a risk for benign polyps to transform into malignant tumors. This risk is influenced by the size and characteristics of the polyps, with larger polyps (greater than 1 cm) or multiple polyps presenting a higher risk. The transformation of polyps into cancers typically requires several years, with most cancers arising from polyps that have existed for 5 to 15 years. Consequently, many physicians recommend regular screenings for early detection of colorectal cancer. The risk of developing colorectal cancer can be mitigated by removing these benign polyps through a procedure known as colonoscopy.
Risk Factors for Colorectal Cancer
Risk factors refer to any attributes or conditions that may increase the likelihood of developing colorectal cancer. As previously noted, the principal cause is not fully understood, and some of these factors can be managed while others cannot, such as age, race, and genetic predisposition. It is important to clarify that having a risk factor does not guarantee cancer will occur; conversely, the absence of risk factors does not ensure immunity against the disease.
General Risk Factors
Common general risk factors associated with colorectal cancer include:
- Age: Colorectal cancer can develop at any age, but the risk increases with advancing age. Typically, diagnoses occur after the age of 50. According to the National Cancer Institute, the average age for a colorectal cancer diagnosis is 68 years.
- Obesity: Being overweight or obese heightens the risk of colorectal cancer in both men and women, with a greater risk observed among men. This risk is often linked to higher levels of abdominal fat. Therefore, maintaining a healthy weight is crucial.
- Diabetes: The presence of diabetes or insulin resistance increases susceptibility to colorectal cancer, particularly type 2 diabetes, which further heightens the risk.
- History of Inflammatory Bowel Disease: Individuals with a history of inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis, face a heightened risk for colorectal cancer. Ulcerative colitis, characterized by long-term inflammation and ulceration of the colon’s inner lining, significantly amplifies the risk compared to individuals without such conditions.
- Personal or Family History of Cancer or Polyps: Having a personal or family history of certain cancers, such as ovarian or uterine cancer, or a history of polyps larger than 1 cm increases risk. Notably, polyps may exist for years prior to a colorectal cancer diagnosis and often do not present symptoms, highlighting the importance of regular screenings, especially for those aged 50 and older.
- Exposure to Radiation: Exposure to radiation targeted at the abdomen, pelvis, or spine during childhood can increase future colorectal cancer risk. Studies indicate that men receiving radiation therapy for prostate or testicular cancer are at a greater risk of developing colorectal cancers.
Genetic Risk Factors
Genetic risk factors associated with colorectal cancer include:
- Race: African Americans tend to have a higher likelihood of developing colorectal cancer and are often diagnosed at more advanced stages compared to other racial groups.
- Family History: A family history of bowel cancer can elevate the risk, particularly if first-degree relatives have been diagnosed before age 55, or if there are multiple family members affected on either side of the family. Specific genetic mutations inherited from parents may also increase susceptibility.
- Hereditary Syndromes: Certain genetic mutations passed through generations can elevate colorectal cancer risk. While the occurrence of cancers due to these hereditary mutations is relatively uncommon, notable syndromes include:
- Familial Adenomatous Polyposis (FAP): Characterized by the presence of hundreds or thousands of polyps in the colon and rectum, which are precursors to cancer.
- Lynch Syndrome: Also known as hereditary nonpolyposis colorectal cancer (HNPCC), this syndrome increases the risk for several types of cancer, including colorectal, uterine, ovarian, stomach, urinary tract, brain, and pancreatic cancers. Cancers associated with Lynch syndrome often grow rapidly and respond poorly to chemotherapy.
Lifestyle Factors
Lifestyle-related factors that increase colorectal cancer risk include:
- Lack of Physical Activity: Sedentary living can contribute to higher colorectal cancer risk, thus regular physical activity is essential. It is recommended that individuals engage in moderate-intensity exercises for at least 30 minutes daily.
- Poor Diet: Diets high in processed and red meats can increase colorectal cancer risk, particularly when cooked at high temperatures, which can generate harmful chemicals. It is advisable to follow a diet rich in fruits, vegetables, and fiber-rich legumes, as these foods provide vitamins, minerals, antioxidants, and other vital nutrients that collectively decrease cancer risk.
- Smoking and Alcohol Consumption: Smoking and excessive alcohol consumption are recognized risk factors for colorectal cancer. Smoking diminishes levels of vitamin C, a powerful antioxidant that combats free radicals linked to cancer development. Therefore, quitting smoking and limiting alcohol intake can significantly reduce the risk of colorectal cancer.
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