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™, 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 the 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

The presence of a colon polyp or tumor may be detected during a colonoscopy or sigmoidoscopy or other examination. These may be done because of symptoms (although early stage colon cancer often causes no symptoms unless the bowel is obstructed) or during a routine screening. Only a biopsy of tissue from the colon polyp or tumor can be used to confirm or rule out the presence of colon cancer. If an unusual growth is found during a colonoscopy or sigmoidoscopy, the doctor can often remove it entirely or take a sample of that growth at the time the procedure is being done.

If other members of your family have had colon or rectal cancer, make sure your doctor knows.  Depending on how many and how close the family members are, your doctor may recommend genetic testing for you to determine whether you might have a genetic mutation that makes you more susceptible to colorectal cancer and whether genetic counseling would be helpful for other members of your family.

When the biopsy confirms a diagnosis of cancer, the biopsy sample also provides the doctor with information about:

• Whether the cancer is non-invasive (localized to 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.

Staging

Staging describes the extent or severity of a cancer diagnosis.  The stage of colon cancer is characterized by 3 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 cancer, also called colon 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. This is also referred to as non-invasive colon cancer. It does not have the potential to spread to other parts of your body so strictly speaking, it is not classified as a malignant polyp.

Colon cancer that is stage I or higher is invasive colon 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 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

The stage of the colon cancer is the foundation on which all NCCN treatment recommendations are based. However, you may require or choose different treatments than someone else with the same stage of cancer. In addition, certain treatment options may be appropriate at one point in your disease but not another. To make the best decisions for yourself, talk to your doctor about the benefits, risks, and possible side effects of the treatment options below.

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.

Surgery

Polypectomy. This is the removal of a polyp during a colonoscopy or sigmoidoscopy examination. If the biopsy of the polyp shows that invasive cancer is present, you may or may not require additional surgery (see “colectomy” below). For polyps with non-invasive cancer, the NCCN Guidelines recommend polypectomy only.

The way a polyp is managed depends on its type:

• Polyps that are flat and grow directly onto the inner wall of the colon are called sessile polyps. Sessile polyps are more difficult to remove than the stalk-like pedunculated type, and a cancerous sessile polyp is more likely to spread to nearby lymph nodes than is cancer in a pedunculated polyp.
• Polyps on stems or stalks that look like mushrooms are called pedunculated polyps.

If a polyp is removed in several pieces, another polypectomy scheduled several months after the initial one may be needed to ensure that the polyp has been completely removed.

The NCCN Colon Cancer Guidelines recommend against additional surgery for a pedunculated polyp that was removed by polypectomy if three criteria are met:

• The polyp has been completely removed in one piece;
• No cancerous tissue is found at the edges of the polyp; and
• The grade of the tumor cells indicates that the tumor is likely to be slow growing.

However, additional surgery is recommended if any of these criteria are not met.

The same recommendations apply if you have a sessile polyp. However, because cancer in a sessile polyp is more likely to spread to lymph nodes, additional surgery may be considered. In this case a colectomy is performed to ensure that any cancer that might have grown beyond the polyp is removed.

Colectomy. This involves removal of the portion of the colon that contains the tumor (or polyp—see section above) as well as some healthy colon tissue on either side of the site of the tumor (or polyp). In addition, lymph nodes in the area near the tumor are also removed. The NCCN Guidelines recommend that at least 12 lymph nodes be removed and examined by a pathologist to adequately check for the spread of cancer.

In many cases, the two ends of the colon will be surgically joined together once the tumor has been removed, and you will have bowel movements as you did before the surgery. In some cases, however, the two portions of the colon are not rejoined; rather, one end of the colon is connected to a collection device outside the body. Waste material is then diverted from the colon into the collection device (usually called a colostomy bag). This may be done to allow the colon to rest and heal, and may be either temporary or permanent. If temporary, another surgical procedure will be needed to reconnect the colon.  Today, few people need to use a colostomy bag for the rest of their lives.

Colon cancer surgery can be done in two main ways:

• Open colectomy: This surgery involves making an opening or incision in the abdomen to expose the colon. Surgery is performed through the incision.
• Laparoscopic-assisted colectomy: This surgery involves the creation of several small openings or incisions in the abdomen. It is less invasive than an open procedure. A scope is placed in one of the openings to guide the surgery by allowing the surgeons to view the interior of the abdomen on a screen in the operating room. Surgical tools are inserted in the other openings to cut away diseased tissue and to extract that tissue. Clinical studies have shown that this type of surgery can be as effective as an open colectomy.

Your doctor may recommend an open colectomy rather than a laparoscopic-assisted colectomy in the circumstances noted below:

• The tumor is blocking your bowel movements
• The tumor has caused a tear in the wall of the colon (a perforated colon)
• There is (are) tumor(s) in the rectum

There are also other reasons why one type of surgery may be a better choice for you. If you are a candidate for a laparoscopic procedure, it is important to find out whether your surgeon is experienced in this approach; clinical studies have shown that the most favorable results with this procedure are at hospitals where laparoscopic surgery has been done many times.

Following your surgery, your doctor likely will recommend that you have a new CT scan so that there is a record of how your bowel looks after cancer is removed.

Some patients report having loose stools after colon cancer surgery.  This is because as part of normal digestion, the colon reabsorbs water.  After surgery, the shorter colon has less room to reabsorb water, so your stools may be more watery than normal.  

Chemotherapy

Chemotherapy drugs are given to destroy or slow the growth of cancer cells. If you are given chemotherapy following surgery it will be called “adjuvant” chemotherapy; adjuvant means to help or assist and is given in addition to surgery to kill any cancer cells that may have spread beyond the tumor. Typically, adjuvant therapy is given for about six months. Studies have shown that adjuvant chemotherapy for colon cancer may increase the likelihood of long-term survival by preventing the cancer from returning.

Not everyone with colon cancer will need to receive chemotherapy. If you have been diagnosed with stage 0, stage I, or stage III colon cancer, the recommendations in the NCCN Guidelines regarding chemotherapy are very clear:

• Chemotherapy is not recommended for those with stage 0 or stage I colon cancer
• Chemotherapy is recommended for those with stage III colon cancer. See Guide to Chemotherapy .

If you have been diagnosed with stage II colon cancer, it is very important that you have a careful discussion with your doctor regarding the risks and benefits of receiving chemotherapy. This discussion is important because clinical studies evaluating the use of chemotherapy in large groups of patients with stage II disease have shown that the benefits of such treatment are minimal when the group is looked at as a whole; however, some groups of patients with stage II disease do benefit from chemotherapy. Therefore, if you have stage II colon cancer it is important that any decisions about chemotherapy are individualized for you and take into account the particular characteristics of your colon cancer diagnosis, your overall health, and your personal preferences. See Guide to Chemotherapy. 

If you have been diagnosed with stage II colon cancer, factors that can influence decision making in support of chemotherapy include:

• Tumor biopsy results have shown that the tumor is grade 3 or 4, meaning that the cancer may have been growing rapidly and might have spread to nearby tissue
• The tumor has caused a tear in the wall of the colon and that tissue may contain cancer cells
• Cancerous tissue is found in the area where the tumor was surgically removed and chemotherapy may destroy the cancer cells
• Fewer than 12 lymph nodes were removed during surgery (because it is harder to tell whether cancer has spread to the lymph nodes if only a small number of lymph nodes have been checked)

 If you have stage II colon cancer and are trying to make a decision about whether or not to get chemotherapy, talk to your doctor about the overall risks and benefits of chemotherapy, rather than asking him or her to make the decision for you. Once you are able to weigh the information, you and your doctor can make the decision that best suits you.

A specific drug or combination of drugs is typically given as adjuvant therapy for colon cancer. These drugs have been tested in patients with your disease and found to be beneficial to a significant number of them.  A list of the chemotherapy regimens that are preferred by the NCCN Colon Cancer Panel can be viewed in the NCCN Colon Cancer Guidelines (see NCCN Clinical Practice Guidelines in Oncology™.)

Some chemotherapy regimens have uncomfortable side effects and include hair loss, intestinal disturbances (including nausea and vomiting), numbness or pain, or a decreased production of certain types of blood cells. Talk to your doctor or oncology nurse about how to manage these effects.

If you are a premenopausal woman, your menstrual periods may stop either temporarily or permanently after you receive chemotherapy, possibly resulting in permanent infertility. Talk to your doctor about what to expect from each treatment and what can be done to help you manage or cope with these side effects.

Radiation therapy

Although radiation therapy (the use of high-energy beams to kill cancer cells) is not typically used in the treatment of colon cancer, your doctor may recommend radiation therapy if the tumor has become attached to another structure in the body or to control bleeding.

Prognosis

In determining a prognosis—the likely course or outcome of a disease—a doctor may look at cancer survival statistics taken from studies of large groups of patients. However, such statistics:

• Are estimates only,
• Can vary widely with each cancer stage,
• Are sometimes based on older data that do not reflect recent advances in early detection and treatment,
• Cannot be used to precisely predict your survival.

Your individual prognosis will be affected by many factors, including:

• Your age,
• Your overall health,
• The stage, and grade of your cancer,
• Your response to the treatment(s) being used.

Ask your doctor which treatment(s), in his or her judgment, will give you the best life expectancy and quality of life. You may want to participate in a clinical trial, in which new and experimental therapies are tested in people with rectal cancer.