Colon Cancer is the 3rd Most Common Type of Cancer
Colon, or large intestine cancer, is among the most frequently diagnosed cancers worldwide. In our country, colorectal cancers rank third among all cancer types.
Colon and Rectal Cancers
The colon and rectum form the large intestine, which is part of the digestive system. The last 20 cm of this section is called the rectum, while the part extending from the rectum to the small intestine is known as the colon. The entire length of the colon is approximately 1.5 meters. The section where the colon meets the rectum is called the sigmoid colon, and the area where it joins the small intestine is called the cecum. Partially digested food passes from the small intestine into the colon. The colon absorbs water and minerals from the food, storing the remaining waste to be excreted through the anus.
Cancer that originates in the colon is called colon cancer, while cancer that starts in the rectum is called rectal cancer. Colon and rectal cancers develop from the cells that make up the inner lining of these organs. They are most commonly diagnosed after the age of 50, with an average onset age of 60. There is no significant difference in prevalence between men and women.
Risk Factors
The exact cause of colorectal cancer is unknown. However, several risk factors are associated with its development:
- Age: Colorectal cancer is primarily seen in older individuals.
- Polyps: Polyps are benign tumors that originate from the inner wall of the colon or rectum. They are common in individuals over the age of 50. Some polyps (adenomas) have the potential to become cancerous. Due to the risk of malignant transformation, polyps should be removed, and regular follow-ups should be conducted. The early detection and removal of polyps significantly reduce the risk of colorectal cancer.
- Family History of Colorectal Cancer: If a close relative (parent, sibling, or child) has had colorectal cancer, the risk of developing the disease increases, particularly at a younger age.
- Genetic Disorders: Mutations in certain genes increase the risk of colorectal cancer. Familial adenomatous polyposis (FAP) is a rare hereditary condition characterized by multiple polyps in the colon and rectum. This condition is caused by mutations in the APC gene. The recommended treatment is the complete removal of the colon. If untreated, individuals with FAP develop colorectal cancer by the age of 40. FAP accounts for less than 1% of all colorectal cancer cases.
- Ulcerative Colitis or Crohn’s Disease: Individuals with these inflammatory bowel diseases have an increased risk of colorectal cancer—up to 10 times higher than the general population.
- Smoking: Smoking increases the risk of developing polyps and colorectal cancer.
Symptoms
- Changes in bowel habits.
- Diarrhea, constipation, or a feeling of incomplete bowel evacuation.
- Blood in the stool (bright red or dark red).
- Narrower-than-normal stools.
- General discomfort in the abdominal area (gas, cramping, bloating).
- Unexplained weight loss.
- Persistent fatigue.
- Nausea and vomiting.
The symptoms and findings of colorectal cancer vary depending on the stage of the tumor. In the early stages, as the tumor grows within the intestine, there may be no symptoms at all. However, as the tumor enlarges and obstructs the bowel, symptoms can range from mild discomfort to an inability to pass gas or stool.
A significant clinical consideration is that the right side of the colon has a wider diameter than the left, meaning symptoms related to obstruction appear later. Tumors in the right side of the colon often cause occult (hidden) blood loss in the stool, leading to anemia, fatigue, shortness of breath, easy tiredness, and changes in bowel habits. Periodic episodes of constipation and diarrhea, abdominal pain, bloating, and weight loss are also common symptoms.
Tumors located closer to the rectum often present with blood in the stool. One important consideration is that rectal bleeding can also occur with hemorrhoids, which may lead to confusion and delay in diagnosis and treatment.
As with other cancers, colorectal cancer may remain asymptomatic until it reaches an advanced stage. Therefore, early detection before symptoms develop is crucial. Screening for colorectal cancer before symptoms appear helps detect polyps and cancer in the early stages. Removing polyps at an early stage can prevent colorectal cancer from developing. When diagnosed early, colorectal cancer is more effectively treated. Thus, individuals over the age of 50 should undergo routine screening, and those at higher risk should begin screening at an earlier age.
Screening Tests for Early Detection
- Fecal Occult Blood Test (FOBT): Since both cancers and polyps can cause bleeding, this test detects small amounts of blood in the stool. However, non-cancerous conditions such as hemorrhoids can also lead to positive results.
- Colonoscopy: This procedure allows visualization of the entire inner wall of the colon and enables the removal of polyps if present. For individuals who are not in high-risk groups, fecal occult blood testing should begin at age 50, and colonoscopy should be performed at least once every five years after the age of 50.
- High-Risk Individuals: Patients who have had polyps removed should undergo a follow-up colonoscopy within 1 to 3 years. Those with a first-degree relative diagnosed with colorectal cancer should begin screening before the age of 40 or 8-10 years before their relative’s diagnosis age. Individuals with familial adenomatous polyposis (FAP) should receive genetic counseling and undergo colonoscopy screenings starting between the ages of 10 and 15.
Op. Dr. Yunus Öztürk
General Surgery Specialist
