Colorectal cancer is a cancer that starts in the rectum or colon, which is the large intestine.These cancers can also be named colon cancer or rectal cancer, depending on where they start. Both of these organs are in the lower portion of your digestive system. The colon is also known as the large intestine, and the rectum is at the end of the colon. Colon cancer and rectal cancer are often grouped together because they have many features in common.
Colorectal cancer is a common disease. According to the American Cancer Society (ACS), an estimated one in 20 people will develop colorectal cancer during their lifetime. Colorectal cancer ranks third in both incidence and cause of cancer death in both men and women in the United States. Global, country-specific data on incidence and mortality are available from the World Health Organization (WHO) GLOBOCAN database.
Researchers don’t know what causes colorectal cancer yet. However, they do know that colorectal cancer develops when healthy cells become abnormal. The abnormal cells divide and multiply faster than they should and don’t die when they should, which is the beginning of cancer.
Most colorectal cancers begin as a polyp or growth on the inner lining of the colon or rectum. Some types of polyps can change into cancer over the course of several years, but not all polyps become cancer. The chance of changing into a cancer depends on the kind of polyp.
The 2 main types of polyps are:
Adenomatous polyps (adenomas):
These polyps sometimes change into cancer. Because of this, adenomas are called a pre-cancerous condition.
Hyperplastic polyps and inflammatory polyps: These polyps are more common, but in general they are not pre-cancerous.
Dysplasia, another pre-cancerous condition, is an area in a polyp or in the lining of the colon or rectum where the cells look abnormal (but not like true cancer cells).
If cancer forms in a polyp, it can eventually begin to grow into the wall of the colon or rectum.
The wall of the colon and rectum is made up of several layers. Colorectal cancer starts in the innermost layer (the mucosa) and can grow through some or all of the other layers. When cancer cells are in the wall, they can then grow into blood vessels or lymph vessels (tiny channels that carry away waste and fluid). From there, they can travel to nearby lymph nodes or to distant parts of the body.
The stage (extent of spread) of a colorectal cancer depends on how deeply it grows into the wall and if it has spread outside the colon or rectum. For more information on staging, see “Colorectal cancer stages.”
It’s important for your doctor to know the stage of your cancer so they can come up with the most effective treatment plan for you and also so they can give you an estimate of the long-term outlook.
Stage 1 of colorectal cancer is the earliest stage. The stages progress up to stage 4, which is the most, advanced stage. The stages of colorectal cancer are:
Stage I cancer penetrates the lining, or mucosa, of the colon or rectum but hasn’t spread to the organ walls.
Stage 2 cancer has spread to the walls of the colon or rectum but hasn’t affected the lymph nodes or nearby tissues yet.
Stage 3 cancer has moved to the lymph nodes but not to other parts of the body yet. Usually, one to three lymph nodes are involved at this stage.
Stage 4 cancer has spread to other distant organs, such as the liver or lungs.
Colorectal cancer is often found after symptoms appear, but most people with early colorectal cancer don’t have symptoms of the disease. This is why it’s important to get the recommended screening tests (described in Colorectal Cancer Prevention and Early Detection) before any symptoms develop.
If your doctor finds something suspicious during a screening exam, or if you have possible symptoms of colorectal cancer, your doctor will recommend exams and tests to find the cause.
Many of the symptoms of colon cancer can also be caused by something that isn’t cancer, such as infection, hemorrhoids, irritable bowel syndrome, or inflammatory bowel disease. In most cases, people who have these symptoms do not have cancer.
Still, if you have any of these problems, it is a sign that you should go to the doctor so the cause can be found and treated, if needed:
Colorectal cancer may not present any symptoms, especially in the early stages. If you do experience symptoms, they may include:
constipation
diarrhea
changes in stool color
changes in stool shape, such as narrowed stool
blood in the stool
bleeding from the rectum
unexplained weakness
passing excessive gas
fatigue
unintended weight loss
abdominal cramps
abdominal pain
If you notice any of these symptoms, make an appointment with your doctor to discuss a colon cancer screening.
When colon cancer does turn out to be the cause, symptoms often appear only after the cancer has grown or spread. That’s why it’s best to be tested for colon cancer before ever having any symptoms. Colon cancer that’s found through screening – testing that’s done on people with no symptoms – is usually easier to treat. Screening can even prevent some colon cancers by finding and removing pre-cancerous growths called polyps.
Your oncologist or cancer doctor uses many tests to find, or diagnose, cancer. Once the cancer is diagnosed, another test is performed to learn if the cancer has spread to other parts of the body. If this happens, it is called metastasis.
For most types of cancer, a biopsy is the only sure way for the doctor to know whether an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.
This list describes options for diagnosing this type of cancer. Not all tests listed below will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:
- The type of cancer suspected
- Your signs and symptoms
- Your age and medical condition
- Your medical and family history
- The results of earlier medical tests
In addition to a physical examination, the following tests may be used to diagnose colorectal cancer.
- Colonoscopy is the endoscopicexamination of the large boweland the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It can provide a visual diagnosis (e.g. ulceration, polyps) and grants the opportunity for biopsy or removal of suspected colorectal cancer lesions. Colonoscopy can remove polyps as small as one millimetre or less. Once polyps are removed, they can be studied with the aid of a microscope to determine if they are precancerous or not. It can take up to 15 years for a polyp to turn cancerous.
If colorectal cancer is found, a complete diagnosis that accurately describes the location and spread of the cancer may not be possible until the tumor is surgically removed.
- Biopsy is the removal of a small amount of tissue for examination under a microscope. A biopsy can make a definite diagnosis of colorectal cancer by evaluation cells. A biopsy may be performed during a colonoscopy, or it may be done on any tissue that is removed during surgery. Sometimes, a CT scan or ultrasound is used to help perform a needle biopsy. A needle biopsy removes tissue through the skin with a needle that is guided into the tumor.
- Molecular testing of the tumor is a test to help identify specific genes, proteins and other factors in the tumor. Results of these tests will help decide whether your treatment options include a type of treatment called targeted therapy. Targeted therapy is a type of cancer therapy that targets the affected area of where there are cancer cells and/or suspected cancer cells.
- Blood tests. Because colorectal cancer often bleeds into the large intestine or rectum, people with the disease may become anemic. A test of the number of red cells in the blood, which is part of a complete blood count (CBC), can indicate that bleeding may be occurring.
Your oncologist may want to order another blood test that detects the levels of a protein called carcinoembryonic antigen (CEA). High levels of CEA may indicate that a cancer has spread to other parts of the body. CEA is not a perfect test for colorectal cancer because levels are high for only about 60% of people with colorectal cancer that has spread to other organs from the colon. In addition, other medical conditions can cause CEA to increase. A CEA test is most often used to monitor colorectal cancer for patients who are already receiving treatment. It is not useful as a screening test. Learn more about tumor markers for colorectal cancer.
- Computed tomography (CT or CAT) scan is used to view the abnormalities or tumors inside of the body using x-rays taken from various angles. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors as well as the size of the growths or tumors. A special dye called a contrast medium can be given before the scan to provide better details of the image. This dye can be injected into a patient’s vein or given as a pill to swallow. CT scans are done before surgery and check the spread of cancer throughout the body.
- Magnetic resonance imaging (MRI). is another medical imaging technique used in radiology to form pictures of the anatomy of the body in both health and disease. But unlike the CAT scan which involve x-rays, the MRI scanners use strong magnetic fields, radio waves, and field gradients to generate images of the inside of the body. MRI can also be used to measure the tumor’s size. Like the CAT scan, a special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill to swallow. According to many oncologists, a MRI is the best imaging test to find where the colorectal cancer has grown.
- Ultrasound is another imaging tool to show the picture of the internal organs. It uses sound waves to find out if cancer has spread to other organs. Endorectal ultrasound is commonly used to find out how deeply rectal cancer has grown and can be used to help plan treatment. However, this test cannot accurately detect cancer that has spread to nearby lymph nodes or beyond the pelvis. Ultrasound can also be used to view the liver, although CT scans or MRIs (see above) are preferred because they are better for finding tumors in the liver.
- Chest x-ray is a fast and painless imaging test that uses certain electromagnetic waves to create pictures of the structures in and around your chest. An x-ray of the chest can help doctors find out if the cancer has spread to the lungs.
- Positron emission tomography (PET) or PET-CT scan. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. It is an imaging test that helps reveal how your tissues and organs are functioning. A PETscan uses a radioactive drug (tracer) to show this activity. The tracer may be injected, swallowed or inhaled, depending on which organ or tissue is being studied by the PET scan. PET scans are not regularly used for all patients with colorectal cancer, but there are specific situations in which your doctor may find them beneficial.
After diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor create a treatment plan tailored to you.
Treatment of colorectal cancer depends on a variety of factors. For example, the state of your overall health and the stage of your colorectal cancer will help your doctor create an effective treatment plan.
Surgery
In the earliest stages of colorectal cancer, it might be possible for your surgeon to remove cancerous polyps through surgery. During surgery, if the polyp hasn’t attached to the wall of the bowels, you’ll likely have an excellent outlook. However, if your cancer has spread into your bowel walls, your surgeon may need to remove a portion of the colon or rectum, along with any neighboring lymph nodes. If at all possible, your surgeon will reattach the remaining healthy portion of the colon to the rectum. If this isn’t possible, they may perform a colostomy. This involves creating an opening in the abdominal wall for the removal of waste. A colostomy is usually temporary.
Chemotherapy
Chemotherapy involves the use of drugs that kill cancerous cells. In the case of colorectal cancer, chemotherapy is a common treatment after surgery to destroy any remaining cancerous cells. Chemotherapy also controls the growth of your tumor and provides symptom relief in late-stage cancer.
Radiation
Radiation uses a powerful beam of high-energy radiation, similar to that used in X-rays, to target and shrink and destroy cancerous cells before and after surgery. Radiation treatment commonly occurs alongside chemotherapy.
Most medical experts recommend a diet low in animal fats and high in fruits, vegetables, and whole grains to reduce the risk of other chronic diseases, such as coronary artery disease and diabetes. Most physicians advise patients to take the following steps:
- Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention. …
- Drink alcohol in moderation, if at all. …
- Stop smoking. …
- Exercise most days of the week. …
- Maintain a Healthy Weight and Control Belly Fat.
Colorectal cancer treatment depends on the size, location, and how far the cancer has spread. Common treatments include surgery to remove the cancer, chemotherapy, and radiation therapy.