What is colorectal cancer?
Colorectal cancer is a term used to refer to cancer that starts in the colon or rectum. Colon and rectal cancers begin in the digestive system, also called the GI (gastrointestinal) system. This is where food is processed to create energy and rid the body of waste matter.
After food is chewed and swallowed, it travels down to the stomach. There it is partly broken down and sent to the small intestine. The word “small” refers to the diameter of the small intestine. The small intestine is really the longest segment of the digestive system. It is about 20 feet long.
The small intestine continues breaking down the food and absorbs most of the nutrients. The small intestine joins the large intestine (large bowel), a muscular tube about five feet long. The first part of the large bowel, called the colon, absorbs water and nutrients from the food and also serves as a storage place for waste matter. The waste matter moves from the colon into the rectum, the final 6 inches of the large bowel. From there the waste passes out of the body through the opening called the anus during a bowel movement.
The colon has 4 sections:
Cancer can start in any of the four sections or in the rectum. The wall of each of these sections (and rectum) has several layers of tissues. Cancer starts in the inner layer and can grow through some or all of the other layers. Knowing a little about these layers is helpful because the stage (extent of spread) of a cancer depends to a great degree on which of these layers it affects.
Cancer that starts in the different areas may cause different symptoms. In most cases, colon and rectum cancers develop slowly over a period of several years. We now know that most of these cancers begin as a polyp – a growth of tissue into the center of the colon or rectum. A type of polyp known as adenomacan canbecome cancerous. Removing the polyp early may prevent it from becoming cancer.
Over 95% of colon and rectal cancers are adenocarcinomas. These are cancers of the cells that line the inside of the colon and rectum. There are some other, more rare, types of tumors of the colon and rectum, but the facts given here refer only to adenocarcinomas.
What causes colorectal cancer?
While we do not know the exact cause of most colorectal cancer, there are certain known risk factors. A risk factor is something that increases a person’s chance of getting a disease. Some risk factors, like smoking, can be controlled. Others, such as a person’s age, can’t be changed. Researchers have found several risk factors that increase a person’s chance of getting colorectal cancer.
What are the risk factors for Colorectal Cancer?
Age: Your chance of having colorectal cancer goes up after age 50. More than 9 out of 10 people found to have colorectal cancer are older than 50.
Having had colorectal cancer before: Even if a colorectal cancer has been completely removed, new cancers could start in other areas of your colon and rectum.
Having a history of polyps: Some types of polyps increase the risk of colorectal cancer, especially if they are large or if there are many of them.
Having a history of bowel disease: Two diseases called ulcerative colitis and Crohn’s disease increase the risk of colon cancer. In these diseases, the colon is inflamed over a long period of time and there may be ulcers in its lining. If you have either of these, you should start being tested at a young age and have the tests often.
Family history of colorectal cancer: If you have close relatives who have had this cancer, your risk is increased. This is especially true if the family member got the cancer before age 60. People with a family history of colorectal cancer should talk to their doctors about how often to have screening tests.
Certain family syndromes: A syndrome is a group of symptoms. For example, in some families, members tend to get a type of syndrome that involves having hundreds of polyps in their colon or rectum. Cancer often develops in one or more of these polyps.
If your doctor tells you that you have a condition that makes you or your family members more likely to get colorectal cancer, you will probably need to begin colon cancer testing at a younger age and you might think about genetic counselling.
Ethnic background: Jews of Eastern European descent (Ashkenazi Jews) have a higher rate of colon cancer
Diet: A diet high in fat, especially fat from animal sources, can increase the risk of colorectal cancer
Lack of exercise: People who are not active have a higher risk of colorectal cancer
Smoking: Most people know that smoking causes lung cancer, but recent studies show that smokers are 30% to 40% more likely than non smokers to die of colorectal cancer. And smoking increases the risk of many other cancers as well.
Alcohol: Heavy use of alcohol has been linked to colorectal cance.
How is colorectal cancer found?
Screening tests are used to look for disease in people who do not have any symptoms. In many cases, these tests can find colorectal cancers at an early stage and greatly improve the chances of successful treatment. Screening tests can also help prevent some cancers by allowing doctors to find and remove polyps that might become cancer. There are several tests used for colorectal cancer:
Stool blood test (fecal occult blood test – FOBT):
This test is used to find small amounts of hidden (occult) blood in the stool. A sample of stool is tested for traces of blood.
A newer kind of stool blood test is known as FIT (faecal immunochemical test). It is very much like the FOBT but is perhaps a little easier to do and it gives a fewer number of false positive results.
Flexible sigmoidoscopy (flex-sig):
A sigmoidoscope is a slender, lighted tube about the thickness of a finger. It is placed into the lower part of the colon through the rectum. This allows the doctor to look at the inside of the rectum and part of the colon for cancer or polyps. Because the tube is only about 2 feet long, the doctor is only able to see about half of the colon. The test can be uncomfortable but it should not be painful. Before the test, you will need to take an enema to clean out the lower colon.
A colonoscope is a longer version of the sigmoidoscope. It allows the doctor to see the entire colon. If a polyp is found, the doctor may remove it. If anything else looks abnormal, a biopsy might be done.
To do this, a small piece of tissue is taken out through the colonoscope. The tissue is sent to the lab to see if cancer cells are present. This test can be uncomfortable. To avoid this, you will be given medicine through a vein to make you feel relaxed and sleepy.
Barium enema with air contrast:
A chalky substance is used to partly fill and open up the colon. Air is then pumped in to cause the colon to expand. This allows good x-ray films to be taken. You will need to use laxatives the night before the exam and have an enema the morning of the exam.
You might think of this as a super x-ray of the colon. Air is pumped into the colon to cause it to expand, and then a special CT scan is done. Right now, this test is not among those recommended by the ACS or other major medical organizations for finding colon cancer early. More studies are needed to find out if it is as good as or better than other methods of finding colon cancer early.
What are the symptoms of colorectal cancer?
Most people with early colon cancer don’t have symptoms. Symptoms usually appear with more advanced disease. If something suspicious turns up as a result of screening or if you have symptoms, you will need further tests. Symptoms of colorectal cancer include:
A change in bowel habits such as diarrhea, constipation, or narrowing of the stool that lasts for more than a few days
A feeling that you need to have a bowel movement that doesn’t go away after doing so
Bleeding from the rectum or blood in the stool (often, though, the stool will look normal)
Cramping or steady stomach pain
Weakness and tiredness
Just because you have these symptoms does not mean you have cancer. But you need to talk to your doctor to be sure. It is also possible to have colon cancer and not have any symptoms.
How do you diagnose colorectal cancer?
If there is any reason to suspect colon or rectal cancer, the doctor will ask you questions about your symptoms and risk factors (take a medical history) and do a physical exam. Then, you will need to have further tests to find out if the disease is really present, and if so, to see how far it has spread. Some of these tests are the same ones that are used for screening people who do not have symptoms.
Your doctor will order a blood count to see if you have too few red blood cells (anemia). People with colorectal cancer often become anemic because of bleeding from the tumor.
You might also have blood tests to check your liver function because colorectal cancer can spread to the liver causing problems. There are other substances (tumor markers) in the blood that can help tell how well treatment is working. But these tumor markers are not used to find cancer in people who have not had cancer and who appear to be healthy; rather, they are most often used for follow-up of people who have already been treated for colorectal cancer.
Biopsy: In a biopsy, the doctor removes a small piece of tissue. The tissue is sent to the lab where it is looked at under a microscope to see if cancer is present.
Ultrasound: Ultrasound uses sound waves to produce a picture of the inside of the body.
CT Scan (computed tomography): A CT scan uses x-rays to take many pictures of the body that are then combined by a computer to give a detailed picture. A CT scan can often show whether the cancer has spread to the liver, lungs, or other organs. CT scans can also be used to help guide a biopsy needle into a tumor.
A new way to use a CT scan is to do a virtual colonoscopy. After stool is cleaned from the colon and the colon is filled with air, a computer can put together a picture of the inside of the colon. This method requires the same preparation as for a colonoscopy and there is some discomfort from the bowel being filled with air. If anything not normal is seen, a follow-up colonoscopy will be needed.
MRI (magnetic resonance imaging):
Like CT scans, MRI displays a cross-section of the body. However, MRI uses radio waves and strong magnets instead of radiation. As with CT scans, a contrast dye may be injected, although this is used less often. MRI scans are helpful in looking at the brain and spinal cord. They take longer than CT scans and you may have to be placed inside a tube. This can feel confining and upset people with a fear of closed spaces.
This test may be done to see whether colorectal cancer has spread to the lungs.
PET scan (positron emission tomography):
In this test, a type of radioactive sugar is used. The cancer cells absorb high amounts of the sugar. PET is useful when your doctor thinks the cancer has spread, but doesn’t know where. PET scans are now more accurate because they can be combined with a CT scan.
For this test, a tube is placed into a blood vessel and moved until it reaches the area to be studied. Then a dye is injected and a series of x-ray pictures is taken. When the pictures are complete, the tube is removed. Surgeons sometimes use this method to find blood vessels next to cancer that has spread to the liver. The cancer can then be removed without causing a lot of bleeding.
Staging of colorectal cancers
Staging is the process of finding out how far the cancer has spread. This is very important because your treatment and the outlook for your recovery depend on the stage of your cancer. For early cancer, surgery may be all that is needed. For more advanced cancer, other treatments such as chemotherapy or radiation therapy may be used.
There is more than one system for staging colon or rectal cancer. Some use numbers and others use letters. But all systems describe the spread of the cancer through the layers of the wall of the colon or rectum. They also take into account whether the cancer has spread to nearby organs or to organs farther away.
Stages are often labelled using Roman numerals I through IV (1-4). In general, the lower the number, the less the cancer has spread. A higher number, such as stage IV (4), means a more serious cancer.
The other tool that doctors use to describe the stage is the TNM system.
TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:
How deeply has the primary (first) tumor penetrated the bowel lining? (Tumor, T)
Has the tumor spread to the lymph nodes? (Node, N)
Has the cancer metastasized to other parts of the body? (Metastasis, M)
For most people, the stage is not known until after surgery, so your doctor may wait until then to assign a number. This will help you both decide on the best treatment for you.
Cancer stage grouping
Doctors assign the stage of the cancer by combining the T, N, and M classifications.
Stage 0: Refers to cancer in situ. The cancer cells are only in the mucosa (the inner lining) of the colon or rectum. Most colorectal cancers at this stage can be treated by polypectomy (removal of the mass of tissue that develops on the inside wall).
Stage I: The cancer has grown through the mucosa and has invaded the muscular layer of the colon or rectum. It has not spread into nearby tissue or lymph nodes (T1 or T2, N0, M0).
Stage IIA: The cancer has grown through the wall of the colon or rectum and has not spread to nearby tissue or to the nearby lymph nodes (T3, N0, M0).
Stage IIB: The cancer has grown through the layers of the muscle to involve the lining of the abdomen (visceral peritoneum). It has not spread to the nearby lymph nodes or elsewhere (T4a, N0, M0).
Stage IIC:The tumor has spread through the wall of the colon or rectum and has invaded neighboring structures. It has not spread to the nearby lymph nodes or elsewhere (T4b, N0, M0).
Stage IIIA: The cancer has grown through the inner lining or into the muscle layers of the intestine and spread to one to three lymph nodes, or to a nodule of tumor in tissues around the colon or rectum that do not appear to be lymph nodes but has not spread to other parts of the body (T1 or T2, N1 or N1c, M0; or T1, N2a, M0).
Stage IIIB: The cancer has grown through the bowel wall or to surrounding organs and into one to three lymph nodes or to a nodule of tumor in tissues around the colon or rectum that do not appear to be lymph nodes but has not spread to other parts of the body (T3 or T4a, N1 or N1c, M0; T2 or T3, N2a, M0; or T1 or T2, N2b, M0).
Stage IIIC: The cancer, regardless of the depth of invasion in the wall of the colon, has spread to four or more lymph nodes, but not to other distant parts of the body (T4a, N2a, M0; T3 or T4a, N2b, M0; or T4b, N1 or N2, M0).
Stage IVA: The cancer has metastasized to a single distant part of the body, such as the liver or lungs (any T, any N, M1a).
Stage IVB: The cancer has metastasized to multiple parts of the body (any T, any N, M1b).
Recurrent: Recurrent cancer is cancer that has come back after treatment
What is the treatment for colorectal cancer?
The treatment of colorectal cancer depends on the size and location of the tumor, whether the cancer has spread, and the person’s overall health.
Treatment based on cancer staging
The usual treatment of stage 0 cancer in situ is a simple polypectomy during a colonoscopy. There is no additional surgery unless the polyp is unable to be fully removed by polypectomy.
If the cancer is stage I, surgical removal of the tumor and lymph nodes is usually the only treatment necessary.
Patients with stage II colon cancer, which involves deeper penetration of the bowel lining without involving the regional lymph nodes, are treated with surgery and some patients are treated with adjuvant chemotherapy.. However, cure rates for surgery alone are quite good, and the benefits of additional treatment are still uncertain for people with this stage of colon cancer.
If the cancer is stage III and has spread to nearby lymph nodes, the treatment usually involves surgical removal of the tumor followed by adjuvant chemotherapy
For patients with stage II or III rectal cancer, radiation therapy is usually offered in combination with chemotherapy, either before or after surgery.
At stage IV, it is usually not recommended that patients have surgery to remove the primary tumor in the colon, unless the tumor is causing physical problems, such as bleeding or blocking the intestines. Standard treatment includes chemotherapy along with a targeted treatment. If possible, surgery to remove metastases (areas where cancer has spread) may also be done. Generally, such surgery is possible if there are a limited number of spots to where the tumor has spread.
The most common treatment for colorectal cancer is surgery to remove the tumor, called surgical resection. Part of the healthy colon or rectum and nearby lymph nodes will also be removed.
Some patients may be able to undergo laparoscopic colorectal cancer surgery. With this technique, several viewing scopes are passed into the abdomen while a patient is under anesthesia. The incisions are smaller and the recovery time is often shorter than with standard colon surgery. Laparoscopic surgery is as effective as conventional colon surgery in removing the cancer. Surgeons who perform laparoscopic surgery have been specially trained in that technique.
Less often, a person with rectal cancer may need to have a colostomy. This is a surgical opening, or stoma, through which the colon is connected to the abdominal surface to provide a pathway for waste to exit the body; such waste is collected in a pouch worn by the patient. Sometimes, the colostomy is only temporary to allow the rectum to heal, but it may be permanent. With modern surgical techniques and the use of radiation therapy and chemotherapy before surgery, most people treated for rectal cancer do not require a permanent colostomy.
Some patients may be candidates for surgery on the liver or lungs to remove tumors that have spread to those organs. An alternative is to use radiofrequency ablation (RFA; energy in the form of radiofrequency waves to heat the tumors). Not all liver or lung tumors can be treated with this approach. In some cases, RFA can be done through the skin. In other cases, RFA can be done during surgery. While this can allow preservation of liver and lung tissue that might be removed in a regular surgical resection, there is also a chance that some portions of the tumor will not be destroyed using this technique.
In general, the side effects of surgery include pain and tenderness in the area of the operation. The operation may also cause constipation or diarrhea, which usually goes away after a while. People who receive a colostomy may have irritation around the stoma. The doctor, nurse, or a specialist in colostomy management (called an enterostomal therapist) can teach the patient how to clean the area and prevent infection.
Many people require retraining of the bowel after surgery; this may require some time and assistance. People should talk with their doctor if they do not regain good control of bowel function.
Radiation therapy is the use of high-energy x-rays to kill cancer cells and is commonly used for treating rectal cancer because this tumor tends to recur locally.
A radiation therapy regimen (schedule) usually consists of a specific number of treatments given over a specific time.
External-beam radiation therapy uses a machine to deliver x-rays to the site of the body where the cancer is located. Radiation treatment is given five days a week for several weeks and may be given in the doctor’s office or at the hospital.
In some cases, specialized radiation therapy techniques, such as intraoperative radiation therapy (a high, single dose of radiation therapy given during surgery) or brachytherapy (placing radioactive “seeds” inside the body), may help eliminate small areas of tumor that could not be removed during surgery.
For rectal cancer, radiation therapy may be used before surgery (called neoadjuvant therapy) to shrink the tumor so that it is easier to remove or after surgery to destroy any remaining cancer cells, as both have shown value in treating this disease
Side effects from radiation therapy may include fatigue, mild skin reactions, upset stomach, and loose bowel movements. It may also cause bloody stools (bleeding through the rectum) or bowel obstruction. Most side effects go away soon after treatment is finished.
Sexual problems, as well as infertility (the inability to have a child) in both men and women, may occur after radiation therapy to the pelvis.
Chemotherapy is the use of drugs to kill cancer cells.
Systemic chemotherapy is delivered through the bloodstream, targeting cancer cells throughout the body A chemotherapy regimen (schedule) usually consists of a specific number of cycles given over a specific time. Chemotherapy for colorectal cancer is usually injected directly into a vein, although some chemotherapy can be given as a pill.
Chemotherapy may be given after surgery to eliminate any remaining cancer cells. In some situations, for rectal cancer, a doctor will give chemotherapy and radiation therapy before surgery to reduce the size of a rectal tumor and lower the chance of cancer returning.
Targeted therapy is a treatment that targets specific genes, proteins, or the tissue environment that contributes to cancer growth and survival. These drugs are becoming more important in the treatment of colorectal cancer.