Colon Cancer: Causes, Symptoms, and Treatment
Medically reviewed by Achuta Uppu, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Colon Cancer?
A gastroenterologist, a doctor who treats the digestive system, often finds colon cancer with a colonoscopy. An oncologist, a cancer doctor, and a colorectal surgeon, a surgeon who operates on the colon, treat it. A direct primary care or concierge doctor can be a first stop for an evaluation and can refer you to a specialist when needed.
What is colon cancer?
Colon cancer is a type of cancer that forms in the tissues of the colon. The colon, also called the large bowel, is the main part of the large intestine. Colorectal cancer starts in the colon or the rectum, which is the end of the colon. It is also sometimes simply called colon cancer.
Nearly all colorectal cancers begin as lumps called polyps in the lining of the colon and rectum. These lumps can slowly develop into cancer.
Symptoms
Many cases of colon cancer have no symptoms. Signs that may be caused by colon cancer or by other conditions include:
- Bright red or very dark blood in the stool.
- Diarrhea, constipation, or other change in bowel habits.
- Pain and tenderness in the lower belly.
- Weight loss with no known reason.
Causes and who gets it
Colon cancer is caused by certain changes in how colon cells grow and divide into new cells.
You have a higher risk of colon cancer if you are age 45 or older. Drinking alcohol, smoking tobacco, and being overweight or having obesity also raise the risk. Your risk is also higher if you eat a lot of red or processed meats. A low-fiber and high-fat diet, or a diet low in fruits and vegetables, also raises risk.
Having a parent, brother, sister, or child with a history of colon or rectal cancer is a risk factor. Some inherited diseases also increase the risk. One of the most common is called Lynch syndrome. Having ulcerative colitis or Crohn disease for 8 years or more also raises the risk. Having a risk factor does not mean that you will get colorectal cancer.
How doctors diagnose it
Your doctor asks about your personal and family health history and does a physical exam. Screening tests can find colon cancer before symptoms start. An abnormal stool screening test should be followed up with a colonoscopy, which can see the entire colon.
A colonoscopy uses a colonoscope to look inside the rectum and colon for polyps, abnormal areas, or cancer. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
Staging is the process used to find out whether cancer has spread within the colon or to other parts of the body.
Treatment
Treatment depends on many things, including the stage of the cancer. Surgery is the most common treatment for all stages of colon cancer.
Stage 0 colon cancer may be treated by removing the tumor with endoscopic surgery. Endoscopic surgery is less invasive surgery using a lighted, flexible tube. For stages I, II, and III, more extensive surgery is needed to remove all or part of the colon and rectum that has cancer. This surgery is called colon resection, or colectomy.
Chemotherapy involves taking medicines that kill cancer cells. Most people with stage III colon cancer receive chemotherapy after surgery for 3 to 6 months. It is given to treat any cancer cells that may remain and to lower the risk that the cancer will come back. Chemotherapy is also used to improve symptoms and prolong survival in people with stage IV colon cancer.
Immunotherapy involves taking medicines that increase the ability of your own immune system to destroy cancer cells.
Cancer treatment can cause problems such as bowel obstruction from surgical scarring. Chemotherapy, immunotherapy, and radiation can cause short- and long-term side effects.
When to see a doctor
Contact your doctor if you have black, tar-like stools, blood during a bowel movement, a change in bowel habits, or unexplained weight loss.
Call 911 or go to the emergency room if you have severe belly pain or pressure, or bleeding that will not stop.
All adults age 45 and older should have a colon cancer screening. People with certain risk factors may need earlier testing, before age 45, or more frequent testing.
How a direct primary care or concierge doctor fits in
A direct primary care doctor charges a flat monthly fee instead of billing insurance, while a concierge doctor usually charges more and often works alongside insurance. If you are 45 or older, talk to your doctor about screening. You can also talk with your doctor if you think you might be at increased risk.
Common questions
Can colon cancer be cured?
Yes, with treatment, stages 0, I, II, and III cancers often are cured. Higher stages of cancer are less likely to be cured. There is a chance that the cancer will come back.
Does colon cancer always cause symptoms?
No, many cases of colon cancer have no symptoms. Screening tests can find colon cancer before symptoms start.
Can screening help prevent colon cancer?
Yes, screening can often find polyps before they become cancerous. Removing these polyps may prevent colon cancer. A healthy lifestyle may also help reduce your risk.
At what age should people start colon cancer screening?
All adults age 45 and older should have a colon cancer screening.
Sources
- MedlinePlus - Colorectal cancer
- National Cancer Institute - Colon Cancer Treatment (PDQ) - Patient Version
- Centers for Disease Control and Prevention - Colorectal Cancer Basics
Medical Disclaimer
This content is for general educational and informational purposes only and is not medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment, and reading it does not create a doctor-patient relationship. Always seek the advice of your physician or another qualified health provider with any questions about a medical condition, and never disregard or delay seeking professional advice because of something you read here. If you think you may have a medical emergency, call 911 (or your local emergency number) immediately.
