The colon and rectum are parts of the digestive system. They form a long, muscular tube called the large intestine (also called the large bowel). The colon is the first four-to-five feet of the large intestine, and the rectum is the last four-to-five inches. Partly digested food enters the colon from the small intestine. The colon removes water and nutrients from the food and stores the rest as waste. The waste passes from the colon into the rectum and then out of the body through the anus.
Risk factors for colorectal cancer
Even though the colon and rectum are two separate organs, most of the cancers found in these structures are of the adenocarcinoma type; thus they are sometimes called “colorectal cancer,” and information on both types is usually presented together. Colorectal cancer is the fourth most common cancer in men and women in the United States. The American Cancer Society estimates approximately 110,000 new diagnoses of colon cancer and 41,000 new diagnoses of rectal cancer per year. The average age at diagnosis is mid-60s.
The exact cause for this cancer has not been found; however, a few risk factors have been identified. Studies have shown that a diet high in fat and low in vegetable consumption may increase the risk for colorectal cancer. Three percent of colorectal cancer patients have one of the two known genetic mutations that greatly increase a person’s chance to develop colorectal cancer. People with a history of benign polyps (called adenomas) and people with a history of inflammatory bowel diseases (such as colitis or Crohn’s disease) have a higher risk of developing colorectal cancer. People with a family history of the disease have a higher risk even if they do not have one of the known genetic mutations.
Diagnosing colorectal cancer
Colorectal cancer is one of the few cancers to have an effective screening method, called colonoscopy. Most colon cancers develop from benign polyps called adenomas. Examining the colon through along lighted tube called a colonoscope enables finding and removing these polyps before they turn into cancerous tumors. The American Cancer Society recommends colon cancer screening for every person over 50 years old, or younger if they have one of the known risk factors listed above.
Treatment of colorectal cancers
Treatment decisions on colorectal cancer depend on staging, which is determined by the size of the tumor, its location, and how far it has spread. Tumors that affect only the inner layer of the colon or rectum are treated only with surgery and have a very high cure rate. As the tumors spread deeper into the colon or rectal wall and to lymph nodes and neighboring organs, the survival rate decreases and more extensive treatments are needed.
Surgery is the primary treatment method for colorectal cancer. The goal of surgery is to remove the sick part of the colon or rectum and maintain normal digestive flow and function. In some cases, however, the surgeon will have to create an opening in the abdomen, called a colostomy, in order to remove waste from the body. In most cases, the colostomy is temporary and would be closed when the colon heals, but for some people, especially those with a tumor in the lower rectum, the colonoscopy could be permanent.
Colon Cancer Surgery
Surgery is the most recommended treatment for colon cancer at an early stage. The cancerous part of the colon and some additional parts on either side of the tumor are removed. Lymph nodes close to the affected region are also removed. The ends of the remaining colon are then connected. This kind of surgery is called colectomy or a segmental resection.
This surgery can be done in many ways:
- Open surgery: Colon is removed by making an incision in the abdomen
- Laparoscopic-assisted colectomy: In this procedure, several small incisions are made in the abdomen through which a long tube like instrument called laparoscope and some surgical instruments are inserted into the colon. The colon and nearby lymph nodes are removed by this procedure.
- Colonscope-assisted colectomy: Early stage colon cancers on the surface of the colon can be surgically removed with the help of a long tube like instrument with light and camera at its end called colonoscope. It is inserted through the rectum. Small surgical instruments are then used to remove the cancer affected colon.
A colostomy is generally not required for colon cancer. Colostomy refers to making an incision in the abdominal region for taking out the excretory matters. In some cases a temporary colostomy is performed.
Surgery for rectal cancer
Surgery is generally the mainstay treatment for rectal cancer. Radiation and chemotherapy may also be used together with surgery.
Types of surgery for rectal cancer:
Operations without cutting the abdomen for early stage rectal cancer
These operations are used only for Stage I rectal cancer.
Polypectomy: It is a procedure of removingmushroom-like growths from the base. These growths are normally seen in Stage 0.
Local excision: It is a procedure of removingsuperficial cancers along with some tissues nearby from the inner surface of rectum.
Local full thickness resection: This procedure involves removal of inner layers of the rectum and some surrounding tissue by cutting through the layers of rectum.
Electrofulgeration: This procedure involves removal of the cancer by using electrical current.
Operations for more advanced stage and some early stage rectal cancer
Different kinds of surgery are done when the cancer has advanced a little more (some Stage I, mostly Stage II and III).
Low anterior resection: Cancer on the upper part of the rectum, which is attached to the colon, isremoved by this surgical procedure. The surgeon also removes additional tissues on both sides of the tumor, tissues surrounding the rectum and nearby lymph nodes. Then the colon is again joined to the rectum.
Proctectomy with colo-anal anastomosis: Cancer on the middle or lower-middle region of the rectum isremoved by this surgical procedure. The surgeon removes the whole rectum and the colon connected with the anus.
Abdominoperineal resection: Cancer on the lower region of the rectum, which is near the anus, isremoved by this surgical procedure. In this procedure, the cancerous region of the rectum and the anus are removed. A colostomy (opening of the colon) is done to remove the excretory wastes in the body.
Pelvic exenteration: When cancer spreads from the rectum to other nearby regions then this procedure is used. It involves removal ofthe rectum, prostate (in male), uterus (in female) and bladder. A colostomy is done to remove the excretory wastes in the body. A urostomy (opening to allow passage of urine) may also be done if the bladder is removed.
Surgery for colorectal cancer that has spread
Colorectal cancer cells that have spread to other organs at advanced stages can be removed surgically for increasing the lifespan of the patients. Besides surgery there are also other procedures like the use of high energy radio waves which may also help to remove cancer which has spread to the liver.
High-energy rays are used to eliminate cancer cells or reduce the size of colon and rectal tumors. This can be done in two ways:
External radiation therapy: A beam of radiation from a machine outside the body is aimed at the affected site of the patient’s body.
Internal radiation therapy or brachytherapy: Radioactive substance sealed in small pellets is placed near the affected region. Cancer cells are killed by the radiations emitted from the radioactive substances. It is normally used for people who cannot undergo surgery.
Radiation therapy may be given before surgery to make the resection of the tumor easier. It may also be given after surgery to kill the cancer cells if they were any left. This reduces the chances of recurrence of cancer. For very advanced stages, radiation therapy may be used for relieving symptoms.
For colon cancer, radiation is mainly used when the cancer has connected to an internal organ or lining of the abdomen. In such cases radiation is given after surgery to ensure that the cancer cells that may have been left behind are killed.
For rectal cancer, radiation therapy can be used as adjuvant or neo-adjuvant therapy.
In some cases of rectal cancer, a small device containing radioactive material is placed in the anus. This causes much less side effect.
In some advanced cases, where the cancer has spread to organs like liver, glass beads coated with radioactive material is injected in the artery that goes to the liver. The bead blocks some small blood vessels that are connected to the tumor and the radioactive emission kills the cancer cells.
Chemotherapy is the use of drugs to treat cancer. It can be used before or after surgery. When given before the surgery its main purpose is to shrink the tumor to make the surgery easier. It is given after the surgery to reduce the chances of recurrence of cancer. Patients with advanced stage tumors may also be given radiation to relieve symptoms. When drugs are administered through a vein or by mouth, then this kind of chemotherapy is called systemic chemotherapy.
Systemic chemotherapy is used when cancer has spread all throughout the body and surgery is not possible. Direct administration of the chemotherapeutic agent to the target organ is called regional chemotherapy. Chemotherapy is the main treatment for stage IV colorectal cancer or metastatic colorectal cancer. Chemotherapy treatment of metastatic colorectal cancer can be done using drugs such as oxaliplatin, fluoropyrimidines, and irinotecan. They are often used in combination.
Side effects of chemotherapy vary with the kind of drugs used and their dosage.
Targeted therapy helps in preventing the growth of tumor cells by blocking some of the enzymes required for cell growth. Several new targeted therapies have been developed recently. The side effects are limited. They are usually given in combination with chemotherapy.
Two epidermal growth factor receptor (EGFR) monoclonal antibodies–cetuximab and panitumumab can cause death of cancer cells. They can be used for the treatment of refractory metastatic colorectal cancer. The angiogenesis (blood vessel formation) inhibitor bevacizumab showed promising results. When used in combination with chemotherapy, the outcome was much better.
Nutrition is a major issue for colorectal cancer patients because treatment may cause many digestive side effects such as poor appetite, nausea, vomiting, diarrhea, or mouth sores.
Colorectal cancer survivors who have a colostomy deal with issues related to body image, intimacy, and sexuality. In men, a certain type of surgery may cause nerve damage and impair sexual function.
Clinical trials refer to those kinds of treatment which are not yet standardized. It is a part of research that aims to develop better strategies for the treatment of cancer. The patients may willingly participate in clinical trials, but cure is not guaranteed.
Marin JJ, Sanchez de Medina F, Castaño B, Bujanda L, Romero MR, Martinez-Augustin O, Moral-Avila RD, Briz O. Chemoprevention, chemotherapy, and chemoresistance in colorectal cancer. Drug Metab Rev. 2012 May; 44(2):148-72.
Chibaudel B, Tournigand C, André T, de Gramont A. Therapeutic strategy in unresectable metastatic colorectal cancer. Ther Adv Med Oncol. 2012 Mar; 4(2):75-89.
García-Foncillas J, Díaz-Rubio E. Progress in metastatic colorectal cancer: growing role of cetuximab to optimize clinical outcome. Clin Transl Oncol. 2010 Aug; 12(8):533-42.
This article was originally published on 7/12/2014 and last revision and update of it was 9/14/2015.
Bub, David S., Susannah Rose, and W. Douglas Wong. 2003. /1 00 Questions and Answers about Colorectal Cancer. Boston: Jones and Bartlett.
Detailed information about colon and rectal cancer is presented in an accessible question-and-answer format. Terms are explained in the sidebar, and the book includes a list of Web sites, organizations, literature, and resources on general and specific topics related to colorectal cancer. This book was co-authored by two colorectal cancer specialists and an oncology
Larson, Carol Ann. 2005. Positive Options for Colorectal Cancer: Self-Help and Treatment. Alameda, CA: Hunter House.
Presented from the perspective of a colon cancer survivor, this book follows the path of a person who received a colorectal cancer diagnosis, starting with a chapter called “Facing the Unknown” and moving to gathering information, working with medical professionals, dealing with feelings, making treatment decisions, possible complications after treatment. Each chapter ends with a list of practical suggestions.
Levin, Bernard, et al. eds., 2006. American Cancer Society’s Complete Guide to Colorectal Cancer. Rev. ed. Atlanta: American Cancer Society.
The American Cancer Society’s all-inclusive guide to colorectal cancer takes a helpful, matter-of-fact approach to explaining risk factors and prevention, screening, diagnosis, symptom management, and treatment options. The book also explores such psychosocial issues as coping with emotions, relationships, and practical issues. Stories from real people with colorectal cancer help personalize the topic.