1. What is colorectal cancer?

The large intestine is the final part of the digestive system and includes the colon and rectum. After food is digested and nutrients are absorbed, the remaining waste moves through the large intestine, where water is absorbed and stool is formed before it is passed out of the body.

Colorectal cancer occurs when abnormal cells in the colon or rectum grow uncontrollably and form a malignant tumor. It is one of the most common cancers worldwide, including in Taiwan. When detected early, colorectal cancer is often highly treatable and outcomes are generally favorable.

2. How does colorectal cancer develop?

Most colorectal cancers develop from colon polyps, particularly adenomatous polyps. Polyps are small growths that develop on the inner lining of the colon or rectum. While most polyps are benign, some may gradually develop into cancer over time.

Because this process often takes years, regular screening and colonoscopy can help detect and remove polyps before they develop into cancer, significantly reducing the risk of colorectal cancer.

3. Common symptoms

In its early stages, colorectal cancer may not cause noticeable symptoms. This is why regular screening is important, even if you feel well.

As the disease progresses, symptoms may include:

• Changes in bowel habits (such as persistent diarrhea or constipation)
• Blood in the stool
• Narrow or ribbon-like stools
• Abdominal pain or discomfort
• Unexplained weight loss
• Loss of appetite
• Fatigue related to anemia
• A lump or mass felt in the abdomen

If you experience any of these symptoms, you should seek medical evaluation.

4. Risk factors

Several factors may increase the risk of developing colorectal cancer:

• Age over 50
• Family history of colorectal cancer or colon polyps
• Personal history of colon polyps
• Diet high in fat and low in fiber
• Frequent consumption of red or processed meats
• Lack of physical activity
• Obesity
• Smoking
• Heavy alcohol consumption
• Inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease

5. Colorectal cancer screening

Early detection through screening can significantly improve treatment outcomes.

In Taiwan, adults aged 50 to 74 years are eligible for a fecal occult blood test every two years through the national colorectal cancer screening program.

If the test result is positive, a colonoscopy is usually recommended to examine the colon and determine whether polyps or tumors are present.

People at higher risk, such as those with a family history of colorectal cancer or previous colon polyps, may need earlier or more frequent screening based on their doctor’s recommendation.

6. Diagnostic tests

If colorectal cancer is suspected, doctors may recommend several tests, including:

• Fecal occult blood test
• Colonoscopy
• Imaging studies such as computed tomography (CT)
• Blood tests and other laboratory studies

Among these tests, colonoscopy is the most important examination for diagnosing colorectal cancer. It allows doctors to directly examine the colon, remove polyps, and collect tissue samples for pathological analysis.

7. Treatment options

Treatment for colorectal cancer depends on the stage of the disease, the location of the tumor, and the patient’s overall health condition.

Common treatment options include:

• Surgery (the primary treatment for many patients)
• Chemotherapy
• Radiation therapy (commonly used for rectal cancer)
• Targeted therapy
• Immunotherapy

Doctors will develop an individualized treatment plan based on each patient’s condition.

8. How can colorectal cancer be prevented?

Adopting healthy lifestyle habits may help reduce the risk of colorectal cancer:

• Eat a balanced diet rich in vegetables, fruits, and fiber
• Limit consumption of red and processed meats
• Exercise regularly
• Maintain a healthy body weight
• Avoid smoking
• Limit alcohol intake
• Participate in regular colorectal cancer screening

9. When should you see a doctor?

You should seek medical advice if you experience:

• Persistent changes in bowel habits
• Blood in the stool
• Narrow stools
• Unexplained weight loss
• Ongoing abdominal pain or discomfort
• Unexplained fatigue or anemia

If these symptoms continue, do not assume they are caused by minor digestive problems or hemorrhoids. Early medical evaluation can help ensure timely diagnosis and treatment.

10. Conclusion

Colorectal cancer is a common disease, but it is also one of the most preventable and treatable cancers when detected early.

Maintaining a healthy lifestyle, participating in regular screening, and seeking medical attention when symptoms occur can help detect colorectal cancer at an earlier stage and improve treatment outcomes.

If you have concerns about your digestive health, discuss appropriate screening and evaluation options with your doctor.