How is colorectal cancer treated?
Colorectal cancer is treated based on the stage of cancer. Staging identifies the severity of the cancer. Treatment options can include the use of surgery, chemotherapy and radiation.
What are the stages of colorectal cancer?
Colorectal cancer is described clinically by the stages at which it is discovered. The various stages of a colorectal cancer are determined by the depth of invasion through the wall of the intestine; the involvement of the lymph nodes (the drainage nodules); and the spread to other organs (metastases). Listed below is a description of the stages of colorectal cancer and the treatment for each stage. In most cases, treatment requires surgical removal (resection) of the affected part of the intestine. For some tumors, chemotherapy or — for rectal cancers — radiation are added to manage the disease.
Stage 0: For lesions that are stage 0 — also known as carcinoma in situ — the disease remains within the lining of the colon or rectum. Lesions are in the pre-cancerous stage and are not cancers. Therefore, removal of the lesion, either by polypectomy via colonoscopy or by surgery if the lesion is too large, may be all that is required for treatment.
Stage I: Stage I colorectal cancers have grown into the wall of the intestine but have not spread beyond its muscular coat or into close lymph nodes. The standard treatment of a stage I colon cancer is usually a colon resection alone, in which the affected part of the colon and its lymph nodes are removed. The type of surgery used to treat a rectal cancer is dependent upon its location, but includes a low anterior resection or an abdominoperineal resection.
Stage II: Stage II is divided into three smaller stages. In the first stage, IIA, the cancer has spread through the wall of the colon. In stage IIB, colorectal cancer has penetrated beyond the muscular layers of the large intestine. By stage IIC the cancer has even spread into adjacent tissue. However, in all stage II lesions, the cancer has not yet reached the lymph nodes. Usually the only treatment for this stage of colon cancer is a surgical resection (removal), although chemotherapy after surgery may be added. For a stage II rectal cancer, a surgical resection is sometimes preceded or followed by chemotherapy and/or radiation.
Stage III: A stage III colorectal cancer is considered an advanced stage of cancer as the disease has spread to the lymph nodes. Once again, there are three smaller stages of stage III colorectal cancer. Stage IIIA is characterized by cancer that has moved beyond the colon wall and spread to one to three lymph nodes or a very early lesion in the colon wall that has spread to four to six lymph nodes. In the second stage, IIIB, more lymph nodes are affected or there is a more advanced lesion in the colon wall with one to three lymph nodes affected. The cancer also impacts the organs in the abdomen in this stage. In stage IIIC, the cancer continues to spread to nearby lymph nodes and impacts more adjacent tissue of organs in the abdomen. For a colon cancer, surgery is usually done first, followed by chemotherapy. Chemotherapy and radiation may precede or follow surgery for a stage III rectal cancer.
Stage IV: For patients with stage IV colorectal cancer, the disease has spread (metastasized) to distant organs such as the liver, lungs or ovaries. This stage is also divided into three stages. Stage IVA is characterized by cancer that has spread to an organ and lymph nodes that are farther from the colon. In stage IVB the cancer has moved to more than one distant organ and more lymph nodes. Stage IVC cancer has impacted not only the distant organs and lymph nodes, but also the tissue of the abdomen. When the cancer has reached this stage, surgery is generally used for relieving or preventing complications as opposed to curing the patient of the disease. Occasionally the cancer's spread is restricted enough to where it can all be removed by surgery. In the case of minimal disease in the liver, the tumor may be treated with radiofrequency ablation (destruction with heat), cryotherapy (destruction by freezing), or intra-arterial chemotherapy. For stage IV cancer that cannot be surgically removed, chemotherapy, radiation therapy, or both may be used to relieve, delay, or prevent symptoms.
What is chemotherapy?
Chemotherapy refers to drugs that kill cancer cells. Chemotherapy drugs can be given intravenously (into a vein) via an injection or a pump, or orally (by mouth) as a pill. Each drug works against a specific cancer and is delivered in specific doses and schedules. Chemotherapy may be recommended for advanced colorectal cancers, in which the cancer cells have spread to the lymph nodes (drainage nodules) or to other organs.
Chemotherapy is used in the following ways:
- Primary chemotherapy is used when the colorectal cancer has already metastasized (spread) to other organs, like the liver or lungs. In this situation, since surgery usually cannot eliminate the cancer, chemotherapy can possibly shrink the tumor nodules, relieve symptoms and prolong life.
- Neo-adjuvant chemotherapy is given before surgery for certain rectal cancers in order to shrink the tumor and allow the surgeon to better remove it. In this situation, the patient usually receives radiation along with the chemotherapy.
- When appropriate, adjuvant chemotherapy is given after the colorectal cancer is removed with surgery. The surgery may not eliminate all of the cancer cells, and some may remain in the lymph nodes or other organs. The adjuvant chemotherapy is used to kill any of these remaining cancer cells.
Your doctor will talk with you about the best treatment for your condition.
What chemotherapy agents are used to treat colorectal cancer?
5-Fluorouracil, or 5-FU (Adrucil®), has been the first-line chemotherapy drug, along with the vitamin leucovorin, for advanced colorectal cancers for many years. 5-FU is often given intravenously but is also available in an oral form as capecitabine (Xeloda®).
Two other intravenous (directly into the vein) chemotherapy drugs — irinotecan (Camptosar®) and oxaliplatin (Eloxatin®) — also are used for the treatment of advanced colorectal cancers. Oxaliplatin is given, along with 5-FU and leucovorin, for advanced colorectal cancers, while irinotecan is used alone or in combination with 5-FU/leucovorin for patients with metastatic colorectal cancer (cancer that has spread).
Newer treatments for metastatic colorectal cancer include monoclonal antibodies and immunotherapy.
Monoclonal antibodies are created in a lab to find and destroy a particular target – in this case, colorectal cancer cells. Because of their precision, the idea is that treating a tumor with a monoclonal antibody will be more specific than chemotherapy drugs, and therefore have fewer side effects.
Some monoclonal antibody medications prevent tumors from growing the blood vessels needed for their survival, such as vascular endothelial growth factor (VEGF), a substance released by tumors to stimulate the growth of new blood vessels. Interfering with the blood supply to a tumor might slow its growth. Others slow cancer growth by targeting the epidermal growth factor receptor (EGFR), a protein found on the surface of about 60 to 80 percent of colon cancer cells. They are often used along with or after other chemotherapy agents for metastatic colorectal cancer that does not respond to other treatments.
What is immunotherapy?
Immunotherapy is a newer type of treatment for colorectal cancer. The goal of immunotherapy is to boost a patient’s immune reaction to the cancer cells to help them fight the disease more effectively. There are two types of immunotherapy: active and passive.
- Active immunotherapy is intended to stimulate the patient’s immune system. The patient’s antibodies (immune system cells) are made to recognize an abnormal component in the cancer cells and then to selectively kill those cells. A vaccine is an example of an active immunotherapy. Active immunotherapy and vaccines against colorectal cancer are still under investigation.
- Passive immunotherapy products are manufactured in a laboratory to imitate the body’s antibodies. Passive immunotherapeutic medications do not stimulate the patients’ immune system to fight the disease. Rather, these man-made antibodies target specific components on the colorectal cancer cells in order to prevent the cancer cells from escaping the body’s natural immune response.
What are the side effects of chemotherapy and immunotherapies?
The side effects of traditional chemotherapy depend upon the drug, its dosage, how long the treatment lasts and the patient. Because traditional chemotherapy drugs target rapidly dividing cancer cells, they also kill other rapidly dividing healthy cells in the lining of the mouth and the gastrointestinal tract, the hair follicles, and the bone marrow. The side effects of chemotherapy come from damage to these normal cells. (Although hair loss is not common to most chemotherapy treatments for colorectal cancer, some people may experience hair thinning.)
The side effects of traditional chemotherapy can include:
- Loss of appetite.
- Hair loss.
- Mouth sores.
Since chemotherapy affects the bone marrow, there may also be a greater risk of infection (because of low white blood cell counts), bleeding or bruising from minor injuries (because of low blood platelet counts), and anemia-related fatigue (because of low red blood cell counts).
Although it may take some time, most side effects related to chemotherapy will go away when the chemotherapy is stopped.
The side effects of monoclonal antibodies depend on the drug. Many of these side effects are similar to those of traditional chemotherapy medications.
Ask your doctor about the side effects of any medications before you start to take them. If you are having any side effects, tell your doctor. In many cases, they can be treated or prevented with medications or a change in diet.