Assuming that polyps are found during a colonoscopy, they can be removed surgically or with the colonoscope. Whether or not actual cancer is found in the colon, the removal of existing polyps is thought to have a preventative function, reducing the risk that any polyps will go on to turn into cancer.

Surgery is generally necessary to remove cancerous polyps or tumors. The earlier cancers can be located, the less extensive the procedures that have to be done in order to remove the cancerous tissues. In early stage cancer, it may be sufficient to remove the inner layers of tissue inside the colon. When tumors have penetrated through the colon wall it can be necessary to remove entire diseased sections of the colon; a process called segmental resection. To the extent that tumors have metastasized, additional involved tissues (nearby lymph nodes, etc.) may need to be removed as well.

When possible, the surgeon will reconnect the healthy colon portions back together so that normal bowel function can be resumed. In some cases this is not possible, however, as in the case where rectum tissues are cancerous. In such cases, the surgeon may have to create a special opening in your abdomen (called a colostomy) which then serves as the new point of elimination of body wastes (stool). Colostomy is sometimes performed on a temporary basis, but it can also become a permanent feature of your battle with cancer.

Common side-effects of colorectal surgery include short-term pain and tenderness as well as diarrhea and constipation. After surgery most patients will need to remain in the hospital for five to seven days with their food intake restricted for the first few days. Most patients fully recover within two months.

In addition to surgery that removes localized cancerous tissues, radiation and chemotherapies may be prescribed as additional treatment to target cancers that may have spread into the body, or for cancer that is inoperable.

Radiation therapy consists of using high energy beams (such as x-rays or gamma radiation) to kill any cancer cells that the surgery may have missed. Radiation is commonly administered externally by aiming highly focused beams at the infected region. Radiation therapy can also be administered by placing radioactive material directly into the body near where inoperable tumors are found. Side effects of radiation therapy, which can include fatigue, bleeding, diarrhea, and loss of appetite, commonly disappear soon after treatment has ended.

Chemotherapy involves the use of powerful anticancer drugs injected directly into the bloodstream or taken by mouth. These drugs are designed to destroy cells that divide rapidly as cancer cells do. Unfortunately cancer cells are not the only cells in the body that divide rapidly. Common side effects of chemotherapy include fatigue, hair loss, nausea, diarrhea, and increased prevalence of infection. However, as is the case with radiation therapy, these side effects tend to go away soon after treatment ends.