What is Colorectal Cancer?

Colorectal cancer starts in the colon or the rectum. These cancers can also be referred to separately as colon cancer or rectal cancer, depending on where they start, though they have many aspects in common.

This type of cancer usually develops slowly over the course of a number of years, often beginning as a non-cancerous polyp on the inner lining of your colon or rectum. Polyps are usually benign, or not cancerous. If not removed, they can evolve into cancer but don’t always. It depends on the type of polyp.

  • Adenomatous polyps (adenomas) are polyps that can change into cancer, and are referred to as pre-cancerous.
  • Hyperplastic polyps and inflammatory polyps are usually not pre-cancerous.

Another kind of pre-cancerous condition is called dysplasia. Dysplasia is an area in the lining of the colon or rectum where the cells look abnormal (but not like true cancer cells) when viewed under a microscope. These cells can change into cancer over time. Dysplasia can also be seen in people who have had diseases such as ulcerative colitis or Crohn’s disease for many years. Both ulcerative colitis and Crohn’s disease cause chronic inflammation of the colon.

Learn More About the Colon

The colon is divided into four sections

Comprehensive Care for Colorectal Cancer

It is our goal to always provide the best and most comprehensive care for colorectal cancer. We work together to identify subtle characteristics of your disease in order to provide an accurate diagnosis and focus on the best treatment options.

Another goal is to do all we can to preserve your quality of life during treatment. We do that by using minimally invasive surgical procedures including laparoscopic and robotic surgery, highly precise radiation therapy techniques, and chemotherapy regimens that are designed to provide you with the best chance to control or cure your cancer, and allow you to maintain your quality of life as much as possible.

At the Saint John’s Cancer Institute, in Santa Monica, California, we are constantly testing new therapies and diagnostic methods for colorectal cancer. We also have access to the latest clinical trials. This means that eligible patients have access to new, experimental treatments and diagnostic approaches not widely available at other hospitals.

If you have recently been diagnosed with colorectal cancer, talking with one of our doctors before you begin any surgery, chemotherapy, or radiation therapy, will offer you the best options for curing or controlling the cancer, while preserving your quality of life. Our surgeons are very skilled at removing the cancer using laparoscopy with a rapid recovery. Also permanent colostomies are rarely performed because our surgeons are experienced in dealing with low rectal cancers and doing sphincter preserving operations.


Colorectal Cancer Diagnosis

The following tests may be used for colon cancer screening or to find out if the cancer has spread. Tests also may be used to find out if surrounding tissues or organs have been damaged by treatment.

  • Digital rectal exam (DRE): The doctor inserts a gloved finger into your rectum to feel for polyps or other problems.
  • Fecal occult blood test (FOBT): This take-home test finds blood in stool.
  • Fecal immunochemical test (FIT): This take-home test finds blood proteins in stool.

Endoscopic Tests:

  • Sigmoidoscopy: A tiny camera on flexible plastic tubing (sigmoidoscope) is inserted into the rectum. This gives the doctor a view of the rectum and lower colon. Tissue or polyps can be biopsied (removed) and looked at under a microscope.
  • Colonoscopy: A longer version of a sigmoidoscope, a colonoscope can look at the entire colon.
  • Endoscopic ultrasound (EUS): An endoscope is inserted into the rectum. A probe at the end bounces high-energy sound waves (ultrasound) off internal organs to make a picture (sonogram). Also called endosonography

Imaging Tests:

  • CT or CAT (computed axial tomography) scan
  • MRI (magnetic resonance imaging) scan
  • PET/CT (positron emission tomography) scan
  • Virtual colonoscopy or CT (computed tomography) colonoscopy
  • Double contrast barium enema (DCBE): Barium is a chemical that allows the bowel lining to show up on an X-ray. A barium solution is given by enema, and then a series of X-rays are taken.

Blood test for carcinoembryonic antigen (CEA): CEA is a protein, or tumor marker, made by some cancerous tumors. This test also can be used to find out if the tumor is growing or has come back after treatment.

Risk Factors

What are the Risk Factors of Colorectal Cancer?

A number of factors can increase a person’s risk of developing colorectal cancer. The good news is that there are steps you can take to protect yourself. In most cases, you can prevent colorectal cancer by undergoing screening to detect and remove polyps from the colon before they become cancerous. This examination is called a colonoscopy.

Many factors can increase your risk of developing colorectal cancer. Some are beyond your control, but others can be affected by your lifestyle.

Learn More About Genetics and Colorectal Cancer

Colorectal Cancer Risk Factors

  • Age:  Most cases occur in people in their 60s and 70s. Cases before age 50 are relatively uncommon unless there is a family history of early colorectal cancer.
  • Polyps:  The presence of polyps in the colon increases risk, especially if they are large or if there are many of them.
  • Personal history of colorectal cancer:  If you’ve previously been diagnosed and treated for colorectal cancer you’re at higher risk for developing it again.
  • Personal history of bowel disease:  Inflammatory bowel diseases (including ulcerative colitis or Crohn’s colitis) increase your risk of colorectal cancer because they inflame the colon over extended periods of time.
  • History of ovarian, uterine, or breast cancer:  Women who have had any of these cancers are at higher risk.
  • Race or ethnic background: African Americans and Jews of Eastern European descent are at higher risk
  • Family history of colorectal cancer:  Someone with a family history of the disease, especially in a parent or sibling before the age of 55 or multiple relatives at any age, is at a higher risk.
  • Genetics:  About 20 percent of colon cancer cases come because of specific genetic mutations. That’s why genetic testing is beneficial.

Colorectal Cancer Online Assessment

For patients who are concerned about inherited family syndromes that cause colon cancer, we offer advanced genetic testing to let you know your risk. Take the online assessment.

Avoid the Following to Reduce the Risk of Colorectal Cancer:

  • A diet that is high in red, processed, or heavily cooked meats.
  • Lack of exercise.
  • Obesity, particularly having excess fat in the waist area, rather than the hips or thighs.
  • Cigarette smoking: Studies indicate that smokers are 30 to 40 percent more likely than nonsmokers to die of colorectal cancer because they are more likely to develop polyps.
  • Too much alcohol consumption.

Colorectal cancer prevention

There are other things you can do to help reduce your risk of developing colorectal cancers, including increasing the amount of these vitamins in your diet:

  • Vitamin D
  • Calcium
  • Magnesium
  • Folic Acid

Aspirin and other NSAIDs

It is possible that aspirin or other non-steroidal anti-inflammatory drugs (NSAIDS) like ibuprofen, as well as some arthritis drugs, may lower the risk of colorectal cancer and polyps. Aspirin may even prevent the growth of polyps in people who were previously treated for early stages of colorectal cancer or who had previously had polyps removed from the colon. However, you should talk with us prior to beginning any NSAID remedy.

Hormone-replacement therapy

It is possible that hormone-replacement therapy (HRT) for women, which consists of estrogen and progesterone and is used after menopause, may also help reduce the risk of colorectal cancer. However, the decision to use HRT is one that should be made between you and your doctor after discussing the potential benefits and risks.

The National Cancer Institute provides current information about risks and benefits of postmenopausal hormone use on their website.


Types of Colorectal Cancers

More than 95 percent of colorectal cancers are adenocarcinomas — cancers of the cells that line the interior of the colon and rectum. Rarer types of tumors include carcinoid tumors, gastrointestinal tumors, and lymphomas.

The type of colorectal cancer you’re diagnosed with will help your physicians decide on the best way to treat your cancer.

Depending on whether you are diagnosed with colon cancer or rectal cancer, your treatment may be slightly different. Because rectal cancer surgery is more complex, due to the narrow confines of the pelvis, we take special care to avoid damaging sexual and bladder nerves as well as a colostomy (bag).


Colorectal Cancer Symptoms

Colorectal cancer can be a preventable disease thanks to screenings like colonoscopies. This test is able to detect polyps in the colon and test them in order to see if they’re benign or malignant.

Unfortunately, colorectal cancer often has no symptoms, making the importance of a colonoscopy even more important. Signs of colon cancer in women and men tend to be the same. In the event that symptoms do occur they may include the following:

  • Rectal bleeding or blood in the stool.
  • A change in bowel habits (such as diarrhea, constipation, or narrowing of the stool) that lasts for more than a few days.
  • Abdominal pain
  • A continuous feeling that you need to have a bowel movement, which does not resolve after passing stool.
  • Weakness

Some of these symptoms may be caused by other conditions, but you should see your doctor if they persist. Any incidence of rectal bleeding or blood in the stool should be brought to your doctor’s attention as soon as possible.


Colorectal Cancer Stages

If you are diagnosed with colon cancer, your doctor will determine the stage of the disease.

Staging is a way of classifying cancer by how much disease is in the body and where it has spread at the time of diagnosis. This helps us to plan the best way to treat the cancer. Once the staging classification is determined, it stays the same even if treatment works or the cancer spreads.

Stage 0:

  • Abnormal cells are found in the inner lining of the colon. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 also is called carcinoma in situ.

Stage 1:

  • Cancer has formed and spread into the first (submucosa) or second (muscle) layers of the rectal wall. It has not spread outside of the rectum.

Stage 2:

  • Cancer has spread outside of the rectal walls into the surrounding fat or nearby tissue. It has not gone into the lymph nodes. It is divided into stages: IIA, IIB or IIC depending on the extent of local tumor involvement.

Stage 3

  • Cancer has spread to nearby lymph nodes. It has not spread to other parts of the body. It is divided into stages IIIA, IIIB or IIIC depending on the extent of local tumor involvement and the number of lymph nodes that contain cancer.

Stage 4

  • Cancer has spread to other parts of the body, such as the liver, lungs or ovaries. It is divided into stages IVA, IVB and IVC depending on the number of different parts of the body to which the cancer has spread.

Colorectal Cancer Treatment


Treatment for colorectal cancer can vary depending on whether the tumor is located in the colon or rectum.

Learn About Our Treatment Options
Surgeons talking

When to See a Provider

Unfortunately, colorectal cancer often has no symptoms, making the importance of a colonoscopy even more important. Guidelines recommend screening for people at average risk should begin at age 45. If you do experience any symptoms, contact your doctor. Any incidence of rectal bleeding or blood in the stool should be brought to your doctor’s attention as soon as possible.