Colonic Cancers
Colon cancer is a type of cancer that begins in the large intestine (colon), which is the final part of the digestive tract. It typically affects older adults, though it can happen at any age. Colon cancer usually begins as small, noncancerous clumps of cells called polyps that form inside the colon. Over time, some polyps can become colon cancers.
Polyps may be small and produce few or no symptoms. Doctors recommend regular screening tests to help prevent colon cancer by identifying and removing polyps before they turn cancerous. If colon cancer develops, treatments such as surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy are available.
Colon cancer is sometimes called colorectal cancer, which combines colon and rectal cancers.
Symptoms
Signs and symptoms of colon cancer include:
- Persistent changes in bowel habits, including diarrhea, constipation, or a change in stool consistency
- Rectal bleeding or blood in stool
- Persistent abdominal discomfort, such as cramps, gas, or pain
- A feeling that the bowel doesn’t empty completely
- Weakness or fatigue
- Unexplained weight loss
Many people experience no symptoms in the early stages. When symptoms appear, they vary depending on the cancer’s size and location in the colon.
When to see a doctor
See a doctor if you notice persistent symptoms. Discuss when to begin colon cancer screening. Guidelines generally recommend screening around age 50, but earlier or more frequent screening may be advised for those with higher risk.
Causes
Most colon cancers begin when healthy cells develop DNA mutations. Damaged cells grow uncontrollably, forming tumors. Cancer cells may invade nearby tissue and metastasize to other body parts.
Risk factors
- Older age (most cases diagnosed over 50)
- African-American race (higher risk)
- Personal history of colorectal cancer or polyps
- Chronic inflammatory bowel diseases (ulcerative colitis, Crohn's disease)
- Inherited syndromes (familial adenomatous polyposis, Lynch syndrome)
- Family history of colon cancer
- Low-fiber, high-fat diet
- Sedentary lifestyle
- Diabetes or insulin resistance
- Obesity
- Smoking
- Heavy alcohol use
- Radiation therapy to the abdomen
Prevention
Screening
Screening can detect colon cancer early or identify polyps before they turn cancerous. Average-risk adults should consider screening around age 50. Higher-risk individuals may need earlier or more frequent screening.
Lifestyle changes
- Eat a variety of fruits, vegetables, and whole grains for fiber, vitamins, and antioxidants
- Drink alcohol in moderation (max one drink/day for women, two for men)
- Stop smoking; seek guidance from your doctor if needed
- Exercise at least 30 minutes most days, start gradually if inactive
- Maintain a healthy weight through diet and exercise; aim for gradual weight loss if needed
High-risk prevention
Some medications, such as aspirin, may reduce risk of polyps or colon cancer in high-risk individuals. Discuss risks and benefits with your doctor.
Diagnosis
Screening
Screening tests for asymptomatic individuals detect early colon cancer or polyps. Colonoscopy can remove polyps before they become cancerous.
Diagnosing colon cancer
- Colonoscopy: visualizes the entire colon, allows biopsy and polyp removal
- Blood tests: assess overall health, liver/kidney function, and carcinoembryonic antigen (CEA) levels
Determining cancer extent (staging)
Imaging (CT scans of abdomen, pelvis, chest) and surgical findings determine cancer stage (0-IV). Stage IV indicates metastasis to other organs.
Treatment
Treatment depends on cancer location, stage, and overall health. Options include surgery, chemotherapy, radiation, targeted therapy, and immunotherapy.
Surgery
Early-stage
- Polypectomy: removal of small, localized cancer during colonoscopy
- Endoscopic mucosal resection: removes larger polyps with a portion of colon lining
- Laparoscopic surgery: minimally invasive removal of polyps or affected colon section
Advanced colon cancer
- Partial colectomy: remove colon segment containing cancer; reconnect healthy portions
- Ostomy: create an opening for stool if reconnection is not possible; may be temporary or permanent
- Lymph node removal for testing
Very advanced cancer
Surgery may relieve blockages or symptoms. In select cases with limited liver or lung spread, localized surgery plus chemotherapy may offer long-term control.
Chemotherapy
Drugs destroy cancer cells. May be used before surgery (shrink tumor), after surgery (kill remaining cells), or to relieve symptoms of unresectable cancer. Shorter courses may reduce side effects in low-risk stage III patients.
Radiation therapy
Uses high-energy sources to kill cancer cells. May shrink tumors before surgery or relieve symptoms when surgery is not an option. Sometimes combined with chemotherapy.
Targeted drug therapy
Targets specific abnormalities in cancer cells, often combined with chemotherapy. Typically for advanced colon cancer.
Immunotherapy
Uses the immune system to fight cancer by counteracting proteins that prevent immune recognition. Reserved for advanced colon cancer.
Supportive (palliative) care
Provides relief from pain and symptoms. Offered alongside curative treatments to improve quality of life and survival.
Coping and support
- Learn about your cancer type, stage, and treatments to make informed decisions
- Maintain close relationships with friends and family for emotional and practical support
- Find a good listener, counselor, or support group for discussing hopes and fears