Colorectal Cancer: Causes, Symptoms, Screening, and Treatments
Introduction
Colorectal cancer is one of the most common cancers worldwide, affecting the colon or rectum — parts of the large intestine. It often begins as small, noncancerous growths called polyps that can gradually develop into cancer over time. Early detection through regular screening significantly improves treatment outcomes.
This article explores the symptoms, risk factors, screening methods, stages, and treatment options for colorectal cancer.
What Is Colorectal Cancer?
Colorectal cancer occurs when abnormal cells form in the lining of the colon (large intestine) or rectum. Over time, these cells can grow uncontrollably, forming tumors that may invade nearby tissues or spread (metastasize) to other organs, such as the liver or lungs.
Colorectal cancer typically develops from adenomatous polyps, which are small, benign clumps of cells. Detecting and removing these polyps early is key to preventing cancer progression.
Colorectal Cancer Predisposing Factors
Several factors can increase the likelihood of developing colorectal cancer.
These are categorized into genetic, lifestyle, and medical risk factors:
1. Genetic and Family Factors
Family history of colorectal cancer or polyps
Inherited syndromes such as Lynch syndrome or Familial Adenomatous Polyposis (FAP)
Genetic mutations affecting DNA repair mechanisms
2. Lifestyle Factors
Low-fiber, high-fat diet
Lack of physical activity
Obesity
Smoking and heavy alcohol consumption
3. Medical Conditions
Chronic inflammatory bowel diseases (ulcerative colitis, Crohn’s disease)
Type 2 diabetes
History of colorectal polyps
Although these factors increase risk, they do not guarantee that cancer will develop. Preventive measures such as healthy diet, regular exercise, and timely screening are highly recommended.
Colorectal Cancer Symptoms
The symptoms of colorectal cancer depend on the location and stage of the tumor. In early stages, symptoms are often mild or absent, which is why regular screening is essential.
Common Symptoms Include:
Persistent changes in bowel habits (diarrhea, constipation, or narrowed stools)
Blood in the stool or rectal bleeding
Unexplained fatigue or weakness
Unintentional weight loss
Abdominal pain, bloating, or cramping
A feeling that the bowel does not empty completely
Anemia (low red blood cell count)
Note: These symptoms may also occur with other digestive conditions, but persistent or unexplained changes should always be evaluated by a medical professional.
Signs and Symptoms of Colorectal Cancer
The warning signs of colorectal cancer are often gradual.
Early signs may include small amounts of blood in the stool or mild discomfort during bowel movements.
As the disease progresses, more noticeable symptoms such as weight loss, fatigue, or persistent abdominal pain may occur.
Because colorectal cancer can grow silently for years, individuals over 45 or those with risk factors should undergo routine screening even without visible symptoms.
Colorectal Cancer Screening
Screening plays a crucial role in early detection and prevention. It can identify precancerous polyps before they become malignant.
Recommended Screening Methods:
Colonoscopy:
The most accurate test for colorectal cancer. A thin, flexible tube with a camera examines the entire colon and rectum. Polyps can be removed during the procedure for biopsy.
Fecal Occult Blood Test (FOBT):
Detects hidden blood in the stool, an early sign of colorectal abnormalities.
Fecal Immunochemical Test (FIT):
Similar to FOBT but more specific for human blood in stool.
Flexible Sigmoidoscopy:
Examines the lower portion of the colon and rectum using a lighted tube.
CT Colonography (Virtual Colonoscopy):
Uses imaging technology to visualize the colon and identify abnormal growths.
Screening Frequency:
Most guidelines recommend beginning screening at age 45 for average-risk adults, or earlier for individuals with family history or genetic risk.
Colonoscopy and Colorectal Cancer
A colonoscopy is both a diagnostic and preventive tool. It allows doctors to:
Detect early-stage cancer or precancerous lesions.
Remove polyps during the same procedure, reducing cancer risk.
The process typically takes 30–60 minutes and is performed under sedation. Preparing for a colonoscopy involves cleansing the bowel the day before to ensure clear visibility.
Staging in Colorectal Cancer
Cancer staging determines how far the disease has spread and helps guide treatment decisions.
Stages:
Stage 0 (Carcinoma in situ): Abnormal cells confined to the inner lining of the colon.
Stage I: Cancer has invaded deeper layers but not spread beyond the colon wall.
Stage II: Cancer extends through the colon wall but hasn’t reached nearby lymph nodes.
Stage III: Cancer has spread to regional lymph nodes.
Stage IV: Cancer has metastasized to distant organs (liver, lungs, etc.).
Staging is determined using imaging tests, biopsies, and pathology reports.
Colorectal Cancer Treatments
Treatment depends on the stage, size, and location of the tumor, as well as the patient’s overall health.
1. Surgery
The primary treatment for localized colorectal cancer is surgical removal of the tumor and affected tissue.
Procedures include:
Polypectomy: Removal of small polyps during colonoscopy.
Local Excision: Removal of early-stage lesions from the colon wall.
Colectomy: Partial or total removal of the colon segment containing cancer.
Rectal Resection: For cancers located in the rectum.
2. Chemotherapy
Uses anti-cancer drugs to destroy cancer cells or prevent their growth. Often used after surgery to eliminate residual cancer cells or in advanced stages to control progression.
3. Radiation Therapy
Employs high-energy rays to target and kill cancer cells. Commonly used for rectal cancer, either before surgery (to shrink tumors) or after (to prevent recurrence).
4. Targeted Therapy
These drugs focus on specific molecules that support cancer cell growth. They are usually prescribed for advanced or metastatic colorectal cancer.
5. Immunotherapy
Helps the immune system recognize and attack cancer cells. It’s typically used in cases with specific genetic mutations such as microsatellite instability (MSI-high) tumors.
Surgeries for Colorectal Cancer
Surgical treatment depends on cancer’s location and extent:
Right or Left Hemicolectomy: Removal of one side of the colon.
Sigmoid Colectomy: Removal of the lower colon section connecting to the rectum.
Abdominoperineal Resection (APR): For lower rectal cancers, involves removing the anus, rectum, and part of the sigmoid colon.
Laparoscopic Surgery: Minimally invasive option with smaller incisions and faster recovery.
All surgical approaches aim to remove cancerous tissue while preserving as much healthy bowel function as possible.
Post-Treatment and Prognosis
The prognosis of colorectal cancer varies depending on early detection, stage, and response to therapy.
Stage I: High survival rate, often exceeding 90%.
Stage II: Approximately 70–80% 5-year survival rate.
Stage III: Around 50–70%.
Stage IV: 10–15%, depending on metastasis sites.
With modern diagnostic tools and personalized treatment, survival rates continue to improve, especially when cancer is detected early.
Preventing Colorectal Cancer
Prevention focuses on lifestyle and medical strategies:
Maintain a diet rich in fruits, vegetables, and fiber.
Reduce red and processed meat consumption.
Engage in regular physical activity.
Avoid smoking and limit alcohol intake.
Schedule routine colorectal screenings starting at age 45.
These actions significantly lower the likelihood of developing colorectal cancer and enhance early detection outcomes.
Key Takeaways
Colorectal cancer is highly treatable when detected early.
Screening with colonoscopy helps identify precancerous polyps.
Recognizing symptoms and seeking timely medical evaluation are vital.
Balanced nutrition and healthy lifestyle choices reduce risk.
Treatment may involve surgery, chemotherapy, radiation, or targeted therapy.
Disclaimer
This article is for educational and informational purposes only and does not constitute medical advice.
Always consult a licensed healthcare provider or gastroenterologist for personalized guidance on screening, diagnosis, or treatment of colorectal conditions