Colorectal Cancer: Causes, Symptoms, and Treatment
Medically reviewed by Achuta Uppu, MD, Internal Medicine. Last reviewed: October 23, 2026.
What kind of doctor treats Colorectal Cancer?
An oncologist (a cancer doctor) usually treats colorectal cancer. A colorectal surgeon (a surgeon for the colon and rectum) also helps. 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 colorectal cancer?
Colorectal cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon). It is also sometimes simply called colon cancer. Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer.
Nearly all colorectal cancers begin as noncancerous lumps in the lining of the colon and rectum. These lumps are called polyps. These polyps can slowly develop into cancer.
Symptoms
Many cases of colon cancer have no symptoms. Colorectal cancer may not cause symptoms, especially at first.
If you do have symptoms, they could include:
- A change in bowel habits, such as diarrhea, constipation, or feeling that the bowel does not empty completely.
- Stools that are narrower than usual.
- Blood in the stool, which may be bright red or very dark.
- Weight loss for no known reason.
These signs may be caused by colon cancer or by other conditions, so check with your doctor if you have them.
Causes and who gets it
Colorectal cancer starts with changes in your DNA, your genetic material. Often, these changes happen during your lifetime and the exact cause is unknown. Anyone can get colorectal cancer, but certain factors make you more likely to develop it.
- Being older. Your risk goes up as you age.
- Having a personal or family history of colorectal cancer.
- Having a genetic syndrome such as Lynch syndrome.
- Having chronic ulcerative colitis or Crohn disease for 8 years or more.
- Having three or more alcoholic drinks per day.
Having one or more of these risk factors does not mean that you will get colorectal cancer.
How doctors diagnose it
If your screening test results are abnormal, you may need more tests to find out if you have cancer. All adults age 45 and older should have a colon cancer screening.
Doctors may use these tests:
- A digital rectal exam, where the provider uses a gloved finger to feel for lumps.
- A colonoscopy, which uses a thin, lighted tube to look inside the rectum and colon for polyps or cancer.
If you are diagnosed with colorectal cancer, more tests will be done to see if the cancer has spread. This is called staging.
Treatment
Treatment depends on many things, including the stage of the cancer.
- Stage 0 colon cancer may be treated by removing the tumor with endoscopic surgery.
- For stages I, II, and III, more extensive surgery is needed.
- The surgery removes all or part of the colon and rectum that is cancerous.
- Chemotherapy uses medicines that kill cancer cells.
- Most people with stage III colon cancer receive chemotherapy after surgery for 3 to 6 months.
- Radiation therapy uses radiation to kill cancer cells.
- Radiation therapy is often used in the treatment of rectal cancer.
- Targeted therapy uses drugs that mainly attack specific cancer cells.
- For rectal cancer, active surveillance means having regular tests to see if the cancer has changed.
With treatment, stages 0, I, II, and III cancers often are cured. Higher stages of cancer are less likely to be cured.
When to see a doctor
Contact your provider if you have black, tar-like stools or blood during a bowel movement. Also contact your provider if you have a change in bowel habits or unexplained weight loss. Call 911 or go to the emergency room if you have severe belly pain, fainting, or bleeding that will not stop.
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. Colorectal cancer may not cause symptoms at first, so screening tests matter. You can talk with your provider about how often you need screening and what type of test you should get.
Common questions
Can colorectal cancer be cured?
Yes, early diagnosis can often lead to a complete cure. In most cases, stage IV cancer is not curable, but there are exceptions, including sometimes when the spread is limited to the liver.
Does colorectal cancer always cause symptoms?
No, many cases of colon cancer have no symptoms. Screening tests can find colon cancer before symptoms start, when the cancer is most curable.
When should I start screening for colorectal cancer?
All adults age 45 and older should have a colon cancer screening. People with certain risk factors may need earlier testing or more frequent testing.
Can polyps lead to colorectal cancer?
Yes, polyps can slowly develop into cancer. Colon cancer screening can often find polyps before they become cancerous. Removing these polyps may prevent colon cancer.
Sources
- MedlinePlus - Colorectal cancer
- MedlinePlus - Colorectal Cancer
- National Cancer Institute - Colon Cancer Treatment (PDQ) Patient Version
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.
