Colon cancer is a common malignancy in the United States. The treatment of patients with colon cancer can be complicated and may require a team of surgical and medical specialists. This review provides general information for patients and their families, covering colon cancer, its risk factors and symptoms, cancer evaluation and staging, and the most common methods of treatment. This review provides general information for patients and their families regarding risk factors, symptoms, cancer evaluation and staging and the most common methods of treatment. Because the treatment and prognosis for rectal cancer often differ from colon cancer, rectal cancer is addressed in a separate review.
WHAT IS THE COLON?
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 4 to 5 feet of the large intestine, and the rectum is the last six inches. Partially digested food enters the colon from the small intestine. The colon removes water and nutrients from the food and turns the rest into waste (stool). The waste passes from the colon into the rectum and then out of the body through the anus (opening).
WHAT IS COLON CANCER?
Cancer begins in cells, the building blocks that make up tissues. Tissues make up the organs of the body. Normally, cells grow and divide to form new cells as the body needs them. When cells grow old, they die, and new cells take their place. Sometimes, this orderly process goes wrong. In patients with colon cancer, new cells form when the body does not need them, and old cells do not die when they should. Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancer that starts in either of these organs may also be called colorectal cancer. These cancer cells have the ability to invade into the wall of the colon or spread to lymph nodes or other organs. Surgical treatment for colon cancer is usually directed at removal of the cancer and lymph nodes near the cancer. Medical treatment of colon cancer is usually an adjunct to the surgical treatment.
HOW COMMON IS COLON CANCER?
In 2012, more than 103,000 people in the United States were diagnosed with colon cancer, making it the fourth most common cancer in both men and women. About 5% of Americans will develop colorectal cancer during their lifetimes. Cancer of the colon is usually preventable, highly treatable, and often curable. Still, over 50,000 Americans die annually from colorectal cancer, making it the second leading cause of cancer-related deaths. Surgery is the primary form of treatment. Patient survival is directly related to the stage of the cancer (how advanced it is). The stage of the cancer is most accurately defined by the pathology report obtained after surgical removal and biopsy of cancerous tissue. The earlier a colon cancer is found and treated, the better. Recurrence of cancerous tissue following surgery is a major problem and is often the ultimate cause of death.
WHAT ARE THE RISK FACTORS FOR COLON CANCER?
No one knows the exact causes of colorectal cancer. Doctors often cannot explain why one person develops this disease and another does not. However, it is clear that colorectal cancer is not contagious. No one can catch this disease from another person. Research has shown that people with certain risk factors are more likely than others to develop colorectal cancer. A risk factor is something that may increase the chance of developing a disease.
- Age over 50: Colorectal cancer is more likely to occur as people get older. More than 90% of people with this disease are diagnosed after age 50. The average age at diagnosis is 72.
- Diet: Studies suggest that diets high in fat (especially animal fat) and low in calcium, folate and fiber may increase the risk of colorectal cancer. In addition, some studies suggest that people who eat a diet very low in fruits and vegetables may have a higher risk of colorectal cancer. However, results from diet studies do not always agree, and more research is needed to better understand how diet affects the risk of colorectal cancer
- Colorectal polyps: Polyps are growths on the inner lining of the colon or rectum. They are common in people over age 50. Most polyps are benign (not cancerous), but some polyps can progress to become cancer. Finding and removing polyps reduces the risk of colorectal cancer.
- Family history of colorectal cancer: First-degree relatives (parents, brothers, sisters, or children) of a person with a history of colorectal cancer are somewhat more likely to develop this disease themselves, especially if the relative had the cancer at a young age. If several close relatives have a history of colorectal cancer, the risk is even greater.
- Genetic alterations: Changes in certain genes increase the risk of colorectal cancer.
- Hereditary nonpolyposis colon cancer (HNPCC) is the most common type of inherited (genetic) colorectal cancer. However, it only accounts for a small percentage of all colorectal cancer cases. It is caused by changes in a specific gene. Most people with an altered HNPCC gene develop colon cancer, and the average age at diagnosis of colon cancer is 44.
- Familial adenomatous polyposis (FAP) is a rare, inherited condition in which hundreds of polyps form in the colon and rectum. It is caused by a change in a specific gene called the APC gene. Unless FAP is treated, it usually leads to colorectal cancer by age 40. FAP accounts for less than 1 percent of all colorectal cancer cases.
- Personal history of cancer: A person who has already had colorectal cancer may develop colorectal cancer a second time, so it is important to follow-up closely with your treating physicians after undergoing treatment. Also, women with a history of cancer of the ovary, uterus, or breast are at a somewhat higher risk of developing colorectal cancer.
- Ulcerative colitis or Crohn’s disease: A person who has had these conditions that cause inflammation of the colon for many years is at increased risk of developing colorectal cancer.
- Cigarette smoking: A person who smokes cigarettes may be at increased risk of developing polyps and colorectal cancer.
If you have colorectal cancer, you also may be concerned that your family members may develop the disease. People who think they may be at risk should talk to their doctor. The doctor may be able to suggest ways to reduce the risk and can plan an appropriate schedule for checkups.
CAN COLON CANCER BE PREVENTED?
Colon cancer is largely preventable. The most important step in preventing colon cancer is getting a screening test. Because of the demonstrated slow growth of most primary lesions, better survival of patients with early-stage lesions, and relative simplicity and accuracy of screening tests, screening for colon cancer should be a part of routine care for all adults aged 45* years or older. Those with close relatives with colorectal cancer should start screening earlier.
Screening tests other than colonoscopy can include testing the stool for blood (hemoccult), fecal DNA, a flexible sigmoidoscopy (shorter scope), or xray (barium and/or air enema or a special type of CT scan). Any abnormal screening test should be followed by a colonoscopy. Colonoscopy involves examination using a flexible lighed instument to examine the entire large bowel. Polyps can be identified and can often be removed during colonoscopy. For this reason, most healthcare providers recommend starting with colonoscopy as the screening test.
There is some evidence that a high fiber, low fat diet might help prevent colorectal cancer.
Family members of people who have HNPCC or FAP can have genetic testing to check for specific genetic changes. For those with detectable abnormalities in their genes, health care providers may suggest ways to try to reduce the risk of colorectal cancer, or to improve the detection of this disease. For some patients, the doctor may recommend an operation to remove all or part of the colon and rectum before developing a cancer.
*In 2018, secondary to new data on the increased risks of colon cancer in those under 50, the American Society of Colon and Rectal Surgery changed recommendations to consider starting screening at age 45.
WHAT ARE THE SYMPTOMS OF COLON CANCER?
Many colon cancers cause no symptoms at all and are detected during routine screening examinations. The most common symptom of colorectal cancer is a change in bowel habits. Many of the symptoms often associated with the disease are not due to cancer. Other common non-cancerous health problems can cause the same symptoms. However, anyone with the following symptoms should see a doctor to be diagnosed and treated as early as possible.
Symptoms of colon cancer may include:
- Having diarrhea or constipation
- Feeling that your bowel does not empty completely
- Finding blood (either bright red or very dark) in your stool
- Finding your stools are narrower than usual
- Frequently having gas pains or cramps, or feeling full or bloated
- Losing weight with no known reason
- Having nausea or vomiting
Usually, early cancer does not cause pain. It is important not to wait to feel pain before seeing a doctor.
HOW IS COLON CANCER DIAGNOSED?
If screening test results suggest cancer or you have symptoms, your doctor must find out whether they are due to cancer or some other cause. Colonoscopy is the most common method for diagnosing colon cancer, although other tests can be suggestive of the diagnosis. During colonoscopy, any abnormal area (such as a polyp) is checked for cancer cells. Often, the abnormal tissue can be removed entirely during colonoscopy. A pathologist checks the tissue for cancer cells using a microscope. Currently, there are no reliable blood tests for diagnosing colon cancer.
ARE THERE DIFFERENT TYPES OF COLON CANCER?
Yes, however, more than 95% of all colorectal cancers are called adenocarcinomas. These cancers arise from cells in the lining of the colon or rectum. When doctors talk about colorectal cancer, this is almost always what they are referring to. The treatment of adenocarcinoma is the focus of this review. Other much less common tumor types include carcinoid tumors, gastrointestinal stromal tumors (GISTs), lymphomas and sarcomas.
HOW IS COLON CANCER EVALUATED AND STAGED?
Once a diagnosis of colon cancer is made, your doctor needs to know the extent (clinical stage) of the disease to plan the best treatment. The stage is based on whether the tumor has invaded nearby tissues, whether the cancer has spread and, if so, to what parts of the body. When colorectal cancer spreads outside the colon or rectum, cancer cells are often found in nearby lymph nodes. If cancer cells have reached these nodes, they may also have spread to other lymph nodes or other organs. After spreading to the lymph nodes, colorectal cancer cells most often spread to the liver. Doctors call this "distant" or metastatic disease.
When cancer spreads from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the original tumor. For example, if colorectal cancer spreads to the liver, the cancer cells in the liver are actually colorectal cancer cells. The disease is metastatic colorectal cancer and not liver cancer. For that reason, it is treated as colorectal cancer, not liver cancer.
When possible, a thorough diagnostic evaluation should be accomplished prior to undergoing treatment for colon cancer. In addition to taking a personal medical and family history and performing a physical exam, your doctor may order the following tests:
- Blood tests: These should include complete cell counts (to check for anemia), standard blood chemistries and CEA (carcinoembryonic antigen) level. CEA is produced by some colon cancers and is useful in detecting cancer recurrence.
- Colonoscopy: Colonoscopy should be performed to evaluate the entire colon and rectum prior to surgery unless the patient’s clinical condition does not allow the colonoscopy to be performed. Colonoscopy provides useful information about the overall health of the colon and allows for biopsy of the cancer and removal of polyps in other areas of the large intestine. In some patients, a radiologic procedure may be used as an alternative test to evaluate the colon prior to surgery.
- CT (computed tomography) scan: An x-ray machine linked to a computer takes a series of detailed pictures of areas inside your body. A CT scan may show whether cancer has spread to the liver, lungs, or other organs. Other imaging tests such as MRI (magnetic resonance imaging) and PET (positron emission tomography) scans; may be ordered by your doctor for specific indications.
Doctors describe colorectal cancer by the following stages:
Stage 0: The cancer is found only in the innermost lining of the colon or rectum. “Carcinoma in situ” is considered to be Stage 0 colon cancer.
Stage I: The tumor has grown into the inner wall of the colon or rectum. The tumor has not grown through the wall.
Stage II: The tumor extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
Stage III: The cancer has spread to nearby lymph nodes, but not to other parts of the body.
Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs.
Often, final staging is not complete until after surgery to remove the tumor, when the lymph nodes can be evaluated for cancer under a microscope.
Advances in colorectal research [Internet]. Besthesda, MD: National Institute of Health, c.2010 Colon cancer; [cited 2013 Dec 10]. Available from: http://www.nih.gov/science/colorectalcancer/
HOW IS COLON CANCER TREATED?
The mainstay of treatment is surgery, and the choice of treatment depends mainly on the location of the tumor in the colon and the stage of the disease. Chemotherapy, or a combination of treatments may also be added. Unlike rectal cancer, radiation therapy is rarely used for colon cancer, although it may have a role in treating advanced or recurrent tumors. Each treatment has certain risks that are described below. The patient may also choose no treatment at all. However, without any treatment, the colon cancer will almost certainly continue to grow and spread to other locations, possibly leading to complete bowel obstruction, perforation of the intestine, and ultimately, death. When colon cancer is diagnosed at a late stage (IV), chemotherapy may be given either as the only treatment or prior to surgery.
HOW IS SURGERY FOR COLON CANCER PERFORMED, AND WHAT IS THE RECOVERY?
Surgical removal of the involved portion of the colon is the most common treatment for colorectal cancer, and it renders many patients disease-free without the need for additional therapy. Two main surgical approaches for treating colon cancer exist:
- Laparoscopy: Colon cancer may be removed with the aid of a thin, lighted tube (a laparoscope) connected to a video screen. Three or four tiny cuts are made into your abdomen. The surgeon sees inside your abdomen with the laparoscope and is able to use small instruments to free the colon up from its attachments in the body. The tumor and nearby lymph nodes are then removed along with part of the healthy colon. The surgeon checks the rest of your intestine and the liver to see if the cancer has spread. The laparoscope may also be used with new approaches to cancer removal such as single port surgery and robotic surgery. Your surgeons can discuss the pros and cons of these new technologies.
- Open surgery: The surgeon makes a larger incision on your abdomen to remove the tumor and part of the healthy colon or rectum. Nearby lymph nodes are also removed. The surgeon checks the rest of your intestine and liver to see if the cancer has spread.
In up to 20% of operations for colon cancer, the surgery cannot safely be accomplished with laparoscopy, so an open operation is performed or a laparoscopic surgery is converted to an open surgery at the same time as the laparoscopic operation. Both techniques require general anesthesia and approximately 4 – 7 days spent recovering in the hospital. Several large studies have demonstrated that both approaches produce equivalent cancer outcomes when performed by surgeons with sufficient training in colorectal surgery. The surgeon removes the colon cancer and the same amount of normal colon and lymph nodes with either approach. There are specific indications for choosing laparoscopy or open surgery; your surgeon will discuss these features with you prior to the operation.
When a section of your colon or rectum is removed, the surgeon can usually reconnect the healthy ends of your intestine. This is called an anastomosis. However, sometimes reconnection is not possible. In this case, the surgeon creates a new path for waste to leave your body. The surgeon makes an opening (stoma) in the wall of the abdomen, connects the upper end of the intestine to the skin, and closes the other end. The operation to create the stoma is called a colostomy. A flat bag fits over the stoma to collect waste, and a special adhesive holds it in place. Less commonly for colon cancer, the small intestine may be used to create a stoma (an ileostomy). For many people, a temporary stoma can be reversed a few months later.
The time it takes to heal after surgery is different for each person. You may be uncomfortable for the first few days. Medicine can help control your pain; you should be comfortable enough to stand and walk with assistance. Before surgery, you should discuss the plan for pain relief with your doctor or nurse. After surgery, your doctor can adjust the plan if you need more pain relief. It is common to feel tired or weak for awhile. Surgery can also cause postoperative constipation or diarrhea. Your surgeon can provide instructions on the management of these conditions. In addition, your health care team monitors you for signs of bleeding, infection, or other problems requiring immediate treatment.
After discharge from the hospital, you should resume light activity such as walking and personal care. Your surgeon may restrict you from lifting heavy objects for a certain time to reduce the risk of developing a hernia (a bulge under your abdominal incision). Generally, you may resume a normal diet, and adequate fluid intake is especially important. Ask your surgeon or nurse prior to discharge about resuming your prior medications in addition to any new medicine you may be taking.
WHAT ARE THE RISKS OF SURGERY FOR COLON CANCER?
Overall, surgery for colon cancer is very safe, with survival in the immediate period after surgery of over 95%. Complications are somewhat more common, occurring in 1 in 5 patients; these can range from minor infections to conditions requiring repeat surgery and prolonged hospital stays. The most common complication is a wound infection at the incision site, typically treated with opening the most superficial layer of the wound and sometimes with antibiotics. This may require the wound opening to be packed daily with gauze as the wound heals. Other potential infections include intra-abdominal infection (abscess), urinary tract (bladder) infections, and pneumonias.
Some patients will develop clots in the veins of their legs called deep vein thromboses (DVTs). Walking soon after your operation helps reduce the risk of DVTs, and most surgeons will also prescribe an injectable medication that is used to reduce the risk of developing blood clots.
A small number of patients may experience heavy postoperative rectal bleeding from the colon anastomosis. The bleeding usually occurs within two weeks of the surgery. You should discuss bleeding risks with your doctor if you plan to resume any pre-surgical blood thinners. If you plan any distant travel after hospital discharge where emergency medical care is difficult to obtain then these plans should be discussed with your surgeon.
Sometimes the connection between the ends of the intestine will leak. This serious problem may be treated with antibiotics, a drain placed through the skin, or a repeat operation that may require a colostomy or ileostomy. Your overall health status before surgery influences the risk of other complications such as heart or breathing difficulties.
AFTER SURGERY, WHAT ADDITIONAL THERAPY IS NEEDED FOR COLON CANCER?
Patients in whom colon cancer is found in the lymph nodes (stage III) or distant locations (stage IV) are normally recommended to undergo chemotherapy after surgery if medically-fit. Chemotherapy uses anticancer drugs to kill cancer cells. Studies have shown that chemotherapy improves long-term survival by reducing the risk of cancer recurrence in patients with stage III colon cancer. Most patients who have colon cancer without spread to lymph nodes or other sites (stage I or II) are treated effectively with surgery alone, although some of these patients with certain risk factors also may benefit from chemotherapy.
Anticancer drugs are usually given through a vein, but some may be given by mouth. Currently, the most common chemotherapy drugs given to patients with colon cancer are 5-fluorouracil (also called 5-FU) and oxaliplatin. Others may be utilized in certain situations, as directed by your medical team. You may be treated several weeks after surgery in an outpatient part of the hospital, at the doctor's office, or at home. Treatment does not usually require overnight hospitalization.
In addition to killing cancer cells, chemotherapy drugs can harm normal cells that divide rapidly. The side effects of chemotherapy depend mainly on the specific drugs and the dose:
- Blood cells: These cells fight infection, help blood to clot, and carry oxygen to all parts of your body. When drugs affect your blood cells, you are more likely to get infections, bruise or bleed easily, and feel very weak and tired.
- Cells in hair roots: Chemotherapy can cause hair loss. Your hair will grow back, but it may be somewhat different in color and texture. Chemotherapy given for colorectal cancer does not generally cause complete hair loss.
- Cells that line the digestive tract: Chemotherapy can cause poor appetite, nausea and vomiting, diarrhea, or mouth and lip sores.
Chemotherapy for colorectal cancer can cause the skin on the palms of the hands and bottoms of the feet to become red and painful. The skin may peel off. Some patients also develop numbness or tingling in their hands and feet. Your health care team can suggest ways to control many of these side effects. Most side effects usually go away after treatment ends.
WHAT FACTORS INFLUENCE OUTCOME AFTER TREATMENT?
The likely outcome of patients with colon cancer is most often related to the stage. Patients with cancer that is confined to the lining of colon have the best prognosis. This is the reason why early detection through screening methods like colonoscopy is so important. Factors such as colon perforation or obstruction, or cancer involvement of other organs, lead to a worse outcome. Some features seen on examination under the microscope after surgery also can influence outcome. Your surgeon will discuss the specific findings with you during first post-operative visit.
WHAT IS THE FOLLOW-UP AFTER TREATMENT FOR COLON CANCER?
Follow-up care after treatment for colon cancer is important. Even after potentially curative surgery and use of additional treatments such as chemotherapy, patients may develop recurrence of the cancer. The risk of recurrence is high if the primary disease is more advanced. Your doctors monitor your recovery and check for recurrence of the cancer. Checkups help ensure that any changes in health are noted and treated if needed. Checkups may include a physical exam (including a digital rectal exam), lab tests (CEA test), colonoscopy, x-rays, CT scans, or other tests. Routine exams generally occur every 3-6 months for a few years, while CT scans or other imaging tests and colonoscopy are performed 1 year after surgery. The frequency of subsequent exams is based upon results of the prior exam.
Colon cancer is a common malignancy that causes a significant number of deaths. However, it is potentially preventable through screening and highly curable with surgery alone when diagnosed at an early stage. Modern chemotherapy continues to improve survival for patients with more advanced stages. The symptoms of colon cancer are vague and, thus, require evaluation by health care professionals. Colon cancer treatment often requires a team of expert physicians, including colorectal surgeons, medical oncologists, radiologists and pathologists. These doctors work with the patient to create the safest and most effective therapy plan.
WHAT IS A COLON AND RECTAL SURGEON?
Colon and rectal surgeons are experts in the surgical and non-surgical treatment of diseases of the colon, rectum and anus. They have completed advanced surgical training in the treatment of these diseases as well as full general surgical training. Board-certified colon and rectal surgeons complete residencies in general surgery and colon and rectal surgery, and pass intensive examinations conducted by the American board of Surgery and the American Board of Colon and Rectal Surgery. They are well-versed in the treatment of both benign and malignant diseases of the colon, rectum and anus and are able to perform routine screening examinations and surgically treat conditions if indicated to do so.
The American Society of Colon and Rectal Surgeons is dedicated to ensuring high-quality patient care by advancing the science, prevention and management of disorders and diseases of the colon, rectum and anus. These brochures are inclusive but not prescriptive. Their purpose is to provide information on diseases and processes, rather than dictate a specific form of treatment. They are intended for the use of all practitioners, health care workers and patients who desire information about the management of the conditions addressed. It should be recognized that these brochures should not be deemed inclusive of all proper methods of care or exclusive of methods of care reasonably directed to obtain the same results. The ultimate judgment regarding the propriety of any specific procedure must be made by the physician in light of all the circumstances presented by the individual patient.
REFERENCES AND ADDITIONAL SOURCES OF INFORMATION
Mutch M and Cellini C. Chapter 41, “Surgical Management of Colon Cancer”. Chapter in Beck DE, Roberts PL, Saclarides TJ, Senagore AJ, Stamos MJ, Wexner SD, Eds. ASCRS Textbook of Colon and Rectal Surgery, 2nd edition. Springer, New York, NY; 2011.
Chang GJ, Kaiser AM, Mills S et al. Practice parameters for the management of colon cancer. Diseases of the Colon & Rectum. 2012; 55:831-843.
The website of the US National Cancer Institute (accessed Aug 2012): http://www.cancer.gov/cancertopics/types/colon-and-rectal
The website of the American Society of Colon & Rectal Surgeons, Ross H, Colon Cancer: Controversies in management of stage II disease. Core Subjects. (accessed Aug 2012):
The website of the American Cancer Society (accessed Aug 2012): http://www.cancer.org/Cancer/ColonandRectumCancer/index
Acknowledgement: ASCRS thanks Sean C. Glasgow, MD for his assistance with the development of this educational brochure.