What is colon cancer?
Colon cancer, also called colorectal or bowel cancer, begins in the large intestine (colon) or rectum. It usually starts as noncancerous growths called polyps on the inner lining of the colon. Over time, some polyps can turn into adenocarcinoma, the most common form of colorectal cancer.
Common symptoms include changes in bowel habits (diarrhea or constipation), rectal bleeding, blood in the stool, abdominal pain, and unexplained weight loss. Risk increases after age 50, in African-Americans, and with a family history or conditions like inflammatory bowel disease.
Causes and risk factors
- Inherited syndromes such as familial adenomatous polyposis (FAP) and Lynch syndrome
- Diets high in red and processed meats, low in fiber
- Physical inactivity and obesity
- Smoking and heavy alcohol use
- Long-term inflammatory bowel disease (ulcerative colitis, Crohn’s disease)
- Type 2 diabetes
- Age over 50 and African-American ethnicity
- Family or personal history of polyps or colorectal cancer
Symptoms
- Persistent change in bowel habits
- Blood (bright red or dark) in stool
- Cramping, gas, or abdominal pain
- Feeling that the bowel does not empty completely
- Unexplained weight loss and fatigue
- Jaundice if spread to liver
- Shortness of breath or bone pain if metastasized
Diagnosis
- Medical history, physical exam, and digital rectal exam
- Stool tests for hidden blood (FOBT, FIT) or DNA changes
- Colonoscopy with biopsy of polyps or suspicious areas
- CT colonography (virtual colonoscopy) or sigmoidoscopy
- Imaging (CT, MRI, PET) to assess spread
- Blood tests including CEA tumor marker and liver function
- Pathology and genetic/molecular analysis of biopsy sample
Treatment
- Surgery (polypectomy, partial or total colectomy, colostomy)
- Chemotherapy (systemic or regional)
- Radiation therapy (external beam or brachytherapy)
- Targeted agents (e.g., bevacizumab, cetuximab, regorafenib)
- Immunotherapy (checkpoint inhibitors for mismatch-repair deficient tumors)
- Ablation and embolization for liver metastases
- Participation in clinical trials of new therapies
- Regular follow-up with colonoscopy, imaging, and blood tests
Sources
- National Cancer Institute. “Rectal Cancer Treatment (PDQ).” Accessed May 28, 2024.
- American Cancer Society. “What Is Colorectal Cancer?” Accessed May 28, 2024.
- Centers for Disease Control and Prevention. “What Can I Do to Reduce My Risk of Colorectal Cancer?” Accessed May 28, 2024.
- Benard F, Barkun AN, Martel M, von Renteln D. World Journal of Gastroenterology. 2018;24(1):124–38. Accessed May 28, 2024.