Colon Cancer

The majority of colon cancers are adenocarcinomas. All other types of tumors detailed below are rarer.

Adenocarcinomas

The most common type of colon cancer, adenocarcinomas are cancerous cells lining the colon’s inner surface. Specifically, they start in the cells tasked with making mucus for lubricating the inside of the colon and rectum. 

Carcinoid tumors

These rare tumors start in the cells that make hormones inside the intestine. For more on this, refer to gastrointestinal carcinoid tumors.

Gastrointestinal stromal tumors (GISTs)

Also uncommon in the colon, gastrointestinal stromal tumors more often occur in other areas of the digestive tract. In cases of colon cancer, GISTs start in the colon wall.

Lymphomas

It’s rare (but not impossible) for cancers of immune system cells (lymphomas) to start in the colon or rectum.

Sarcomas

Sarcomas starting in the wall of the colon and rectum are rare. For more on this, refer to soft tissue sarcoma.

Exactly what causes colon cancer is unknown, but a number of controllable and non-controllable factors may contribute to the likelihood of developing the disease. 

In the United States, the most common colon cancer risk factors include the following:

Controllable risk factors

• Being overweight or obese
• Frequently eating red meats or processed meats
• Lack of physical activity
• Smoking, especially long-term
• Heavy alcohol use (more than two drinks per day)

Non-controllable risk factors

Age

The risk of developing colon cancer increases after age 50.

History of colorectal polyps

People who have a history of adenomatous polyps, or who have had colorectal cancer before, have an increased risk.

Inflammatory bowel disease

Inflammatory bowel diseases, such as ulcerative colitis or Crohn’s disease, cause inflammation in the lining of the colon, which raises the risk of cancer.

Family history

Having a family history of colon cancer, or adenomatous polyps, is linked to an increased risk.

Inherited gene mutations

A small percentage of colon cancers may be linked to genetic mutations passed down in families.

Talk to your doctor about your risk and whether you should consider genetic counseling.

Screening tests can often detect colon cancer at its earliest stages, when treatment is most likely to be successful. But an estimated 1 in 3 people between ages 50 and 75 don’t get screened, according to the Colon Cancer Alliance.

Recommended screenings for women and men at average risk of developing colorectal cancer should begin at age 50. If you have an increased risk of colon cancer, your physician may recommend screening earlier.

The most common colon cancer screening tests, procedures and frequency for people at average risk are:

Colonoscopy

The physician inserts a flexible, lighted tube with an attached camera through the patient’s anus to examine the rectum and the entire colon while the patient is under sedation. Colonoscopy is the most thorough screening exam, and often allows the doctor to remove polyps as well. This test is recommended every 10 years.

Flexible sigmoidoscopy

During a flexible sigmoidoscopy, the physician inserts a flexible, lighted tube with an attached camera through the patient’s anus to examine the rectum and lower part of the large intestine (sigmoid colon) while the patient is under sedation. This test should be repeated every five years, or every three years with FOBT.

High-sensitivity fecal occult blood test (FOBT)

This test checks for hidden blood in three consecutive stool samples. This test should be repeated every year.

If you’re 50 or older — or you’re younger than 50 and have risk factors — talk with your physician about the right screening approach.

Colon cancer may not always cause symptoms, especially in the early stages. If symptoms are present, they may include the following:

• A change in bowel habits — such as diarrhea, constipation or narrowing of the stool — that lasts for more than a few days
• Feeling the need to have a bowel movement, even after you have had one
• Bleeding from the rectum with bright red blood
• Blood in the stool
• Cramping or abdominal pain
• Weakness and fatigue
• Unintended weight loss
• Low red blood cell counts (anemia) caused by blood loss through the rectum

Having any of these symptoms doesn’t mean you have colon cancer. Stomach viruses, infections and the flu often cause similar symptoms. If your symptoms persist or become worse, let your doctor know so that you can find the cause and any potential health problems.

Diagnosing colon cancer can include certain types of imaging tests, a biopsy and laboratory tests. Specific imaging tests may include:

Biopsy

Biopsy involves removal of a small sample of suspicious tissue. The sample, which can be taken during a colonoscopy or sigmoidoscopy, is tested and examined by pathologists in a lab.

Computed tomography (CT) scan

A CT scan is a form of X-ray imaging test that captures images of the body from different angles. The images are combined to create detailed cross-sectional views of organs, bones and blood vessels.

Abdominal ultrasound

Abdominal ultrasound uses high-frequency sound waves that reflect off body structures and are then translated by a computer to create digital images. Ultrasound does not expose patients to any radiation.

Endorectal ultrasound

Endorectal ultrasound relies on a transducer inserted into the rectum and can be used to determine how far a tumor has penetrated immediate tissues and if it has spread to nearby organs or lymph nodes.

Magnetic resonance imaging (MRI)

MRI relies on a powerful magnet, radio waves and advanced digital technology to provide detailed images of organs, bone and soft tissue.

Positron emission tomography (PET) scan

A PET scan involves imaging after the patient swallows a type of radioactive sugar that existing cancer cells will quickly absorb so they can be identified under a special camera. This scan combined with a CT scan to give physicians the ability to view a picture of potentially cancerous areas through the PET while also seeing more detailed images from a CT scan.

The wall of the large intestine has several layers, as well as numerous blood and lymph vessels. Colon cancer stages indicate how far the cancer may have grown into the wall of the intestine and beyond to other parts of the body. This helps doctors determine the best course of treatment.

Stage 0

Stage 0 colon cancer is when abnormal cells are found in the mucosa (innermost layer) of the colon wall. These abnormal cells may become cancer. Stage 0 is also called carcinoma in situ.

Stage I

Stage I colon cancer is when cancer has formed in the mucosa of the colon wall and has spread to next layer of tissue under the mucosa. Cancer may have spread to the muscle layer of the colon wall.

Stage IIA

Stage IIA colon cancer is when cancer has spread through the muscle layer of the colon wall to the outermost layer.

Stage IIB

Stage IIB colon cancer is when cancer has spread through the outermost layer of the colon wall, but not to nearby organs.

Stage IIC

Stage IIC colon cancer is when cancer has spread through the outermost layer of the colon wall to nearby organs.

Stage IIIA

• Cancer has spread through the mucosa to the next layer of tissue and may have spread to the muscle layer. Cancer has spread to at least one but not more than three nearby lymph nodes, or cancer cells have formed in tissues near the lymph nodes; or
• Cancer has spread through the mucosa to the next layer of tissue and has spread to at least four but not more than six nearby lymph nodes.

Stage IIIB

• Cancer has spread through the muscle layer of the colon wall to or through the outermost layer, but not to nearby organs. Cancer has spread to at least one but not more than three nearby lymph nodes, or cancer cells have formed in tissues near the lymph nodes; or
• Cancer has spread to the muscle layer of the colon wall or to the outermost layer, and has spread to at least four but not more than six nearby lymph nodes; or
• Cancer has spread through the mucosa to the next layer of tissue and may have spread to the muscle layer. Cancer has spread to seven or more nearby lymph nodes.

Stage IIIC

• Cancer has spread through the outermost layer of the colon wall, but not to nearby organs. Cancer has spread to at least four but not more than six nearby lymph nodes; or
• Cancer has spread through the muscle layer of the colon wall to or through the outermost layer, and has spread to seven or more nearby lymph nodes; or
• Cancer has spread through the outermost layer of the colon wall and has spread to nearby organs. Cancer has spread to one or more nearby lymph nodes, or cancer cells have formed in tissues near the lymph nodes.

Stage IVA

Stage IVA is when cancer may have spread through the colon wall and to nearby organs or lymph nodes. Cancer has spread to one organ that is not near the colon, such as the liver, or to a distant lymph node.

Stage IVB

Stage IVB is when cancer may have spread through the colon wall and to nearby organs or lymph nodes. Cancer has spread to more than one organ that is not near the colon, or into the lining of the abdominal wall. 

No one wants to hear that they have cancer. You may feel frightened, overwhelmed, anxious or sad. All of these feelings are perfectly normal. The more you learn about your diagnosis and next steps, the sooner you can begin to make informed decisions about your treatment.

Questions and considerations

Your cancer care team offers a wealth of information for the many questions that come with a colon cancer diagnosis. Here are some you might want to bring up with your physician or health insurance provider:

• Should I get a second opinion?
• How do I find a specialist?
• What is my treatment plan?
• Will I have to miss work/school?
• What are the side effects of colon cancer treatment?
• How successful is my treatment likely to be?
• What costs will be covered by insurance?
• Which costs will I be responsible for?

Your Scripps team is here to help you find the answers you need to take an active role in your care. In addition, there are a number of community resources that provide education, information and helpful resources — often at no cost.

Learn more about the many cancer patient resources available to you and your loved ones.

A multidisciplinary team of Scripps gastrointestinal specialists, oncologists, surgeons, pathologists, nurses and clinicians will work with you to provide the most appropriate and personalized treatment for your individual case. Plus, we’ll partner you with a nurse navigator who will help coordinate your care and ensure you get the support you need throughout your treatment and recovery. For more on how Scripps puts you at the center of care, visit Why Scripps.

When colon cancer is detected early, surgery is the most common and effective treatment. In many cases, pre-cancerous polyps and small tumors that are detected during a screening colonoscopy can be removed during the procedure.

Treatment for more advanced colon cancers can include a combination of surgery and chemotherapy or radiation therapy, depending on the size of the tumor, how close it is to sensitive tissues and other organs, the patient’s age and general health, and whether the cancer is new or returning.

Colon cancer surgery

If colon cancer has not spread to other parts of the body, surgery is usually the primary treatment. These surgeries can be traditional open surgeries or minimally invasive, such as laparoscopic surgery or robotic-assisted surgery.

• Polypectomy and local excision involves the removal of early stage colon cancer during removal of polyps while using a colonoscope. It does not require an abdominal incision and includes removal of a small amount of surrounding tissue near the diseased area.
• Laparoscopic-assisted colectomy involves when a device with a small video camera that provides the surgeon a view inside the body. In this minimally invasive procedure, Scripps surgeons make several small incisions, then insert long instruments to remove part of the colon and lymph nodes.
• Minimally invasive robot-assisted surgery is when Scripps surgeons perform a colectomy using robotic tools inserted through small incisions. The robotic system uses a magnified, 3-D high-definition camera and tiny instruments that give the surgeon greater range of mobility and dexterity than their own hands and wrists. The movements of the advanced robotic tool are completely controlled by the surgeon.
• Open colectomy involves a single incision in the abdomen through which part of the colon and lymph nodes near the cancer are removed. The surgery is sometimes referred to as partial colectomy, segmental resection or hemicolectomy.

If colon cancer has spread to nearby organs — such as the prostate, bladder, colon or gynecologic organs — those organs may be removed during surgery as well.

Radiation therapy for colon cancer

Most patients with colon cancer do not need radiation therapy. In some cases, radiation therapy is used if the tumor can’t be entirely removed surgically or if there are concerns for positive margins following surgery. Sometimes, targeted radiation therapy, such as radiosurgery, can be offered to treat cancer that has spread to a limited area beyond the colon (such as for bone, liver or lung metastases). Additionally, radiation therapy can be offered to help control pain or symptoms caused by cancer that has spread to other areas. 

Radiation therapy may be offered along with chemotherapy for more advanced colon cancer, either before surgery or after surgery, to help reduce the risk of the cancer coming back locally.

Scripps has the most comprehensive radiation therapy offerings in San Diego, including 3-D conformal radiation therapy and intensity-modulated radiotherapy (IMRT). 

• 3-D conformal radiation therapy allows physicians to visualize a patient’s anatomy in 3-D though the use of advanced computer software to match the radiation dose to the shape of the tumor while minimizing exposure of surrounding healthy tissues and organs.
• Intensity-modulated radiation therapy (IMRT) is an advanced form of radiation therapy that allows the radiation oncologist to specify the dose of radiation for the tumor while restricting the dose to surrounding healthy tissues. 

Chemotherapy and infusion services

Chemotherapy may be used as part of a treatment plan to shrink colon cancer tumors before surgery. It’s most often used after surgery with an aim of attacking cancer cells that have already spread to the lymph nodes.

Because advanced colon cancer has the ability to spread beyond your colon and metastasize to other areas within the abdominal cavity, Scripps physicians may use a procedure called hyperthermic intraperitoneal chemotherapy (HIPEC) for rare cases in which cancer involves the peritoneum, or lining of the abdomen. HIPEC treatment includes direct circulation of chemotherapy drugs heated to 107° F (42° C) into the patient’s abdominal cavity for 90 minutes before surgical wounds are closed and treatment is completed.

Some colon cancer treatment plans involve clinical trials. Talk with your physician about whether a clinical trial is right for you. See our list of clinical trials that are currently enrolling patients.

Your Scripps cancer team will develop a customized treatment plan outlining the treatments and therapies we recommend for your care. Before you begin treatment, you and your physician will review your plan together and discuss any questions or concerns you may have.

Your colon cancer treatment plan generally includes:

• Family and medical history
• A summary of your cancer diagnosis and staging information
• Diagnostic testing completed (e.g., imaging, biopsy, lab tests)
• Plans for surgery, radiation, chemotherapy and/or other treatments
• Potential side effects of treatments
• Contact information for your cancer care team members

Along with helping you understand your course of treatment and encouraging discussion between you and your physician, your plan helps your team coordinate your care. You also can share your treatment plan with other providers who may be involved in your medical care.

Your colon cancer care team includes health and medical professionals from a wide range of specialties. Scripps will customize your team to ensure you have the expertise and support you need. 

Your team may include:

• Gastroenterologists
• Surgeons and surgical oncologists
• Radiation oncologists
• Medical oncologists
• Registered nurses
• Nurse navigators
• Dietitians
• Oncology social workers

For specific details on Scripps Cancer Center's multidisciplinary approach to treatment, visit your cancer care team.

In support of our patients, survivors, their family members and the community, we host a handful of cancer support groups as well as a range of free workshops and health and wellness events on a number of topics such as:

• Nutrition
• Expressive writing
• Yoga
• Meditation

Check the current list of support offerings or contact your oncology social worker or cancer care coordinator.

For info about other cancer support groups in the San Diego community, call the American Cancer Society at 800-227-2345.