Cancer of the colon or rectum is the third most frequently diagnosed cancer in men and women in the U.S. Cancer of any portion of the large intestine is sometimes collectively referred to as colorectal cancer.
If you have been diagnosed with colon cancer, you probably have many questions and concerns about treatment. This patient summary, which is based on the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines™), will help you understand the best available treatments for colon cancer. Talk to your doctor about these therapies so that together you can decide on a treatment plan that is right for you.
Background
The colon is part of the body’s digestive system. The digestive system removes and processes nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and anal canal.
Most colon cancers are believed to start as a polyp, a small abnormal growth in the lining of the colon. However, most colon polyps will not turn out to be cancerous.
People who have a family history of colorectal cancer may have a slightly higher risk of developing the disease than do others. Smoking, a diet high in animal fat (and low in fiber), a history of having many noncancerous polyps in the colon, and other factors also increase a person’s risk for colorectal cancer. In addition, some of these factors may increase the risk that colorectal cancer will recur (come back) after treatment.
Diagnosis
Colorectal cancer may cause symptoms related to changes in bowel habits such as diarrhea or constipation, feeling that your bowel does not empty completely, finding blood (either bright red or very dark) in your stool, and/or finding your stools are narrower than usual. These symptoms may be caused by a noncancerous or cancerous tumor or noncancerous polyps. Many of these symptoms may also be due to other problems e.g., hemorrhoids, anal fissures, irritable bowel syndrome, etc. Sometimes, no symptoms may be present.
The presence of a colon polyp or a tumor may be detected during a colonoscopy or sigmoidoscopy or other test or examination; these may be done because of symptoms or as part of a routine screening when no symptoms are present. Only a biopsy of tissue from the colon polyp or tumor can confirm or rule out the presence of cancer. If an unusual growth is found during a colonoscopy or sigmoidoscopy, the doctor can often either remove it entirely or take a sample of that growth at the time the procedure is being done.
The Pathology Report
When the biopsy confirms the diagnosis of cancer, the sample provides the doctor with additional important information about:
- Whether the cancer is non-invasive (localized to the layer of tissue where it began) or invasive (has spread deeper into the wall of the colon).
- The grade of the tumor cells, that is, how much the cancer cells resemble healthy cells under a microscope. Generally, grade 1 colon cancer cells look more like healthy cells and grow slowly while grade 4 cells have more pronounced abnormalities and grow quickly.
Your tumor will also be tested for a KRAS mutation in its cells. The presence or absence of this marker will be used to help determine the type of treatment that is most likely to be effective for you.
More Testing
If colorectal cancer is found, you will be scheduled for tests that will help your doctor determine whether your tumor is localized to the area where it began (that is, it is localized) or whether it has spread (metastasized). Your doctor also will take a detailed medical history and may request other tests to determine your health and whether certain treatments are appropriate for you. In general, the tests that you will have will include:
- A complete blood count
- Tests to determine the health of your liver and kidneys
- CT scan of your chest, abdomen, and pelvis
- Colonoscopy, if not already done or if the previous colonoscopy could not be completed because of an obstruction in the colon
Staging
A formal system called staging is used to identify how localized or widespread your cancer is. Stages range from 0 (most localized) to IV (spread to distant organs in your body). Staging is an important part of developing the best treatment plan for you. For a fuller discussion of staging, click here.
The stage of a colon cancer is characterized by three factors:
- How deeply the tumor has penetrated into the wall of the colon
- Whether cancer has spread to surrounding lymph nodes, and if so, the number of lymph nodes affected
- Whether there is evidence of distant spread of disease (metastasis)
Stage 0 colon or rectal cancer, also called colon or rectal cancer “in situ” (which means “in place”), is a very early stage of disease that has not spread beyond the innermost lining of the colon or rectum. This is also referred to as non-invasive colorectal cancer. Colon or rectal cancer that is stage I or higher is invasive colon or rectal cancer. In stage I or stage II disease, there is no lymph node involvement and no distant spread of disease. The defining characteristic of stage III is that cancer is detected in one or more surrounding lymph nodes. Stage IV colon or rectal cancer is characterized by evidence of distant disease spread (metastasis). (Read a separate summary on Colon and Rectal Cancer - Stage IV.)
The stage is described more precisely with a lettering system. For example, a colon cancer tumor staged as IIB has penetrated more deeply into the wall of the colon than a stage IIA colon cancer tumor.
Treatment
While all colon or rectal cancers are cause for concern, the effectiveness of treatment depends on how localized the cancer is and whether or how far it has spread in your body. Other factors that affect your outlook and treatment plan are the characteristics of your tumor cells such as KRAS status and the grade of your tumor, as well as your age general health.
In general, the more localized your cancer is, the better the chance is that it can be cured by treatment. If the cancer has spread to different parts of your body, the chances for cure are significantly reduced; however, with treatment, it may be controlled and you may live a high quality life for years.
Depending on stage of your disease, the characteristics of your tumor, and your general health, your treatment will include one or more of the following: surgery, radiation therapy, chemotherapy, and/or targeted therapy. These are discussed in relevant treatment sections.
Your doctor should provide you with a written care plan explaining what treatments you will have, when they will occur and how often if you are receiving chemotherapy or radiation, and what type of side effects you may experience. Some side effects can be anticipated and you can be given pretreatment to minimize them. You will be asked to sign an informed consent indicating that you have been told about your treatment and what to expect. It is very important that you ask your doctor or nurse every question you have. Cancer and its treatment are complicated and most patients have questions.
Life After Treatment
When you therapy is completed, you will enter follow-up: You will see your doctor at regular intervals to make sure that you remain healthy and that any long-term effects of colon or rectal cancer or its treatment can be attended to.