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CancerICD-10: C18.9About 153,000 new cases diagnosed annually in the U.S.

Colorectal Cancer

Also known as: Colon Cancer, Rectal Cancer, Bowel Cancer, CRC

Colorectal cancer is cancer that begins in the colon or rectum and is the third most common cancer diagnosed in both men and women. Most colorectal cancers develop from precancerous polyps that grow on the inner lining of the colon or rectum over 10-15 years. Regular screening through colonoscopy can detect and remove polyps before they become cancerous, making colorectal cancer one of the most preventable cancers.

Symptoms

Change in bowel habits (diarrhea, constipation, or narrowing of stool) lasting more than a few days
Rectal bleeding or blood in the stool
Persistent abdominal cramping, pain, or discomfort
Unexplained weight loss
Fatigue and weakness
Feeling that the bowel doesn't empty completely
Iron-deficiency anemia of unknown cause

Causes

  • Mutations in colon or rectal cells, often starting in polyps
  • Genetic syndromes (Lynch syndrome, familial adenomatous polyposis)
  • Chronic inflammatory bowel disease (ulcerative colitis, Crohn's disease)
  • Accumulation of DNA damage over time

Risk Factors

  • Age 45 and older (risk increases significantly with age)
  • Family history of colorectal cancer or polyps
  • Personal history of inflammatory bowel disease
  • Diet high in red and processed meats
  • Obesity, physical inactivity, and smoking
  • Heavy alcohol use

Diagnosis

  • Colonoscopy with biopsy (gold standard for diagnosis)
  • Fecal immunochemical test (FIT) for occult blood
  • Stool DNA test (Cologuard)
  • CT colonography (virtual colonoscopy)
  • CEA blood test for monitoring (not screening)

Treatment

  • Surgical removal of the tumor (colectomy or local excision)
  • Adjuvant chemotherapy (FOLFOX, CAPOX) for stage III cancer
  • Radiation therapy, particularly for rectal cancer
  • Targeted therapy (bevacizumab, cetuximab) for advanced disease
  • Immunotherapy (pembrolizumab) for MSI-high tumors
  • Polypectomy for precancerous polyps during colonoscopy

Prevention

  • Get screened starting at age 45 (or earlier if high-risk)
  • Eat a diet high in fruits, vegetables, and whole grains
  • Limit red and processed meat consumption
  • Maintain a healthy weight and exercise regularly
  • Limit alcohol and avoid smoking

When to See a Doctor

  • You experience persistent changes in bowel habits
  • You notice blood in your stool or rectal bleeding
  • You have unexplained weight loss, fatigue, or iron-deficiency anemia
  • You are 45 or older and have not been screened for colorectal cancer

Frequently Asked Questions

Related Conditions

Crohn's Disease

Autoimmune

Diverticulitis

Digestive

Anemia

Metabolic

Celiac Disease

Autoimmune

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

Content reviewed against peer-reviewed medical literature and clinical guidelines. Read our editorial standards.