Understanding Colon Cancer -- Diagnosis and Treatment

Medically Reviewed by Melinda Ratini, MS, DO on March 30, 2023

Both the U.S. Preventive Services Task Force and the American Cancer Society say that people with average risk for colorectal cancer should start getting tested for it at age 45.Screening tests include the following options:

Stool-based tests:

  1. Guaiac fecal occult blood test every year
  2. Fecal immunochemical test (FIT) every year
  3. FIT + stool DNA test every 3 years

Direct visualization tests:

  1. Colonoscopy every 10 years
  2. Flexible sigmoidoscopy every 5 years
  3. CT colonography (virtual colonoscopy) every 5 years

You can also ask your doctor about newer tests such as:

Cologuard. You collect a sample of your stool at home and send it to a laboratory. Technicians there check the DNA in your stool to look for gene changes linked to colorectal cancer. They also look for blood, which can be a sign of cancer. Cologuard is the only FIT + stool test available in the U.S.

Capsule colonoscopy. You swallow a double-ended capsule that holds a tiny wireless video device that shows your colon as it passes through your body. You don’t need to be put to sleep for this procedure, but you’ll have to prepare your bowel before swallowing the capsule. It helps your doctor find polyps, but they can’t take out any tissue this way. The FDA has approved capsule colonoscopy only for patients who had an incomplete colonoscopy.

If you have a positive result on a screening test that is not a colonoscopy, you should get a colonoscopy to check your entire colon. Any polyp or mass or abnormal growth found by colonoscopy will result in a biopsy, in which tissue will be tested for cancer. 

If a biopsy finds cancer, you may have imaging tests using X-rays and CT scans of your abdomen, pelvis, and chest to find out whether the cancer has spread to other parts of your body.

Your doctor will also do blood tests to find out how well your liver and kidneys are working, to look for anemia, and to measure the level of carcinoembryonic antigen (CEA) in your blood. It’s often higher in people who have colorectal cancer, especially if it has spread.


Colorectal cancer treatment involves not only therapies to cure or control the disease but methods to manage your emotional and physical needs. Quality of life is a central issue for doctors, as it should be for your loved ones.

Many complementary cancer therapies can be helpful when you use them along with standard medical treatment. But complementary therapies should never replace traditional care.

The main types of treatment for colorectal cancer are surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy. Depending on the stage of the cancer, these treatments may be combined.

Surgery is the most effective treatment for local colorectal tumors. Very small tumors can be removed during a colonoscopy. But even in these cases, the best treatment is often removing the part of the colon where the tumor is, the fat around it, and nearby lymph nodes. Your doctor may do surgery laparoscopically or by the open method, which uses larger cuts.

Your doctor can usually reattach the healthy sections of colon and rectum. But if they can’t, they’ll make an opening, known as a stoma, in your belly and attach the severed colon to it. You collect solid waste in a bag worn over the stoma. This procedure, known as a colostomy, often is only temporary. Once the bowel has had time to heal, a second operation reconnects the colon and rectum. You may be more likely to need a permanent colostomy if you have rectal cancer, since it might be harder to keep your rectum.

Soon after surgery, your doctor will probably give you painkillers and other medications to ease temporary diarrhea or constipation. They’ll recommend nutritious foods, rich in calories and proteins, so you can heal and grow stronger.

Radiation therapy is treatment with high-energy rays that destroy cancer cells. For rectal cancer, radiation is usually given after surgery, along with chemotherapy, in order to destroy any cancer cells that were left behind. This is called adjuvant therapy. Radiation can also be used along with chemotherapy in order to shrink a tumor, making surgery easier. This is known as neoadjuvant therapy. In advanced rectal cancer, radiation can shrink tumors that cause bowel obstruction, bleeding, or pain.

You might get radiation therapy if you have colon cancer and the tumor has attached to another organ in your belly, or if a tumor is found near the margins of the cancer that was removed.

Chemotherapy drugs treat various stages of colorectal cancer. They include 5-fluorouracil, capecitabine (Xeloda), irinotecan (Camptosar), oxaliplatin (Eloxatin), and the combination drug trifluridine and tipiracil (Lonsurf). Chemotherapy can be given directly into your liver if colon cancer has spread there.

Targeted therapy drugs work in a different way. They block the cancer’s blood supply or block a protein or gene change that the cancer has made to help it grow. They can treat colorectal cancer that has spread (or metastasized) to other parts of your body. These drugs include amucirumab (Cyramza), bevacizumab (Avastin), cetuximab (Erbitux), encorafenib (Braftovi), entrectinib (Rozlytrek), larotrectinib (Vitrakvi), panitumumab (Vectibix), regorafenib (Stivarga), and ziv-aflibercept (Zaltrap). A combination of two targeted drugs, tucatinib (Tukysa) and trastuzumab (Herceptin), may be used for people with advanced colorectal cancer that produces an excess amount of a protein called HER2.

Immunotherapy involves drugs that stimulate your immune system to recognize and destroy cancer cells. Ipilimumab (Yervoy), nivolumab (Opdivo), and pembrolizumab (Keytruda) are medications called immune checkpoint inhibitors and are sometimes used to treat advanced colorectal cancer.

Follow-up exams are crucial to make sure cancer doesn’t come back after treatment. But hundreds of thousands of people live comfortable, regular lives after colorectal surgery and colostomy.

Show Sources


American Cancer Society.

National Cancer Institute.

FDA: "FDA approves new treatment for advanced colorectal cancer,” “Ramucirumab mCRC,” “Trifluridine/tipiracil.”

CDC: “Colorectal (Colon) Cancer: What Should I Know About Screening?”

American Cancer Society: “Colorectal cancer screening tests,” “Colon Cancer Screening: What Are the Options?”

Spada, C. Therapeutic Advances in Gastroenterology, May 2012.

National Comprehensive Cancer Network: “NCCN Guidelines for Patients: Colon Cancer.”

National Cancer Institute: “Regorafenib.”

Wilhelm, S.M. International Journal of Cancer, published online April 22, 2011.

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