Colon cancer is cancer of the large intestine (colon), the lower part of the digestive system. Rectal cancer is cancer of the last several inches of the colon. Together, they're often referred to as colorectal cancers. Most cases of colon cancer begin as small, noncancerous (benign) clumps of cells called adenomatous polyps. Over time, these polyps may become cancerous.
Colon cancer symptoms
Polyps can be small and produce few, if any, symptoms. Some of the most common symptoms of colon cancer can be categorized as gastrointestinal distress. They include:
- Chronic constipation or diarrhea
- Blood on the surface of the rectum
- Blood in the stool
- A persistent urge to pass stool
- Changes in the frequency or consistency of one’s bowel movements
- Having thin, ribbon-like stools
- Cramping or bloating
- An inability to fully empty the bowels
If your signs and symptoms indicate that you could have colon cancer, your doctor may recommend diagnostic tests and procedures such as a colonoscopy, labs and radiology studies.
Screening for colon cancer
Screening tests are used to look for disease in a person who is not exhibiting any symptoms. As colon cancer most often develops from noncancerous polyps, having regular screenings allows doctors to remove these polyps before they have a chance to turn cancerous.
The U.S. Preventive Services Task Force (USPSTF) recommends that all adults ages 45 to 75 receive regular colorectal cancer screenings. Those at increased risk of colon cancer should receive screenings earlier than age 45. This includes individuals that:
- Are closely related to someone diagnosed with colorectal cancer
- Have inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
- Have been diagnosed with familial adenomatous polyposis (FAP) or Lynch syndrome
If you are at increased risk, speak to your doctor about when you should begin colon cancer screenings and which test is the right option for you.
Diagnosing colon cancer
Often, the first step of diagnosing colon cancer is a physical examination. Your doctor will ask about your medical history and palpate your abdomen to feel for any masses or lumps. A digital rectal exam—in which your doctor inserts a gloved finger into the rectum to locate any abnormal areas—may also be part of the physical exam. If the results of this exam indicate the possibility of a colon cancer diagnosis, further testing may be recommended.
Some of the various diagnostics used in diagnosing colon cancer include:
- Stool tests, including fecal occult blood tests and fecal immunohistochemistry tests
- Blood tests, including complete blood count (CBC) panels, liver enzyme tests and tumor marker tests
- Imaging tests, such as CT scans and MRIs
- Diagnostic colonoscopies
- Endoscopic ultrasounds
- Molecular tests
Types of colon cancer
Colon cancer can develop in several different types of cells within the large intestine. The condition subtype is designated by the cell type in which it originates. The main forms of colon cancer include:
- Adenocarcinomas, which develop in the colon’s mucus-producing glands
- Gastrointestinal stromal tumors, or GISTs, which develop in the interstitial cells of Cajal that line the colon’s interior walls
- Carcinoid tumors, which develop in the hormone-producing cells in the large intestine
- Lymphomas, which develop in the immune system cells
- Sarcomas, which develop in the muscles, connective tissues and blood vessels of the colon
Stages of colon cancer
Once you've been diagnosed with colon cancer, your doctor will order tests to determine the extent (stage) of your cancer, which will inform your treatment plan. Colon cancer can be classified as stage 0 to stage 4:
- Stage 0 indicates cancer cells have been found in the lining of the colon, but have not spread to nearby lymph nodes or tissues.
- Stage 1 indicates cancer cells have been found in the lining of the colon and connective tissues beneath the colon’s mucous membrane, but not in any nearby lymph nodes or tissues.
- Stage 2 indicates cancer cells have grown through the wall of the colon or layers of muscles lining the abdomen (visceral peritoneum), but have not spread to nearby lymph nodes or elsewhere in the body.
- Stage 3 indicates that the cancer has grown to surrounding organs and lymph nodes, but isn’t present in distant parts of the body.
- Stage 4 indicates that the cancer has spread to distant areas of the body, such as the lungs, liver or lining of the abdomen.
Treating colon cancer
The three primary treatment options for colon cancer are surgery, chemotherapy and radiation therapy. Treatment typically involves a combination of two or more of these options. Thanks to advancements in cancer treatment, there are even more options available to colon cancer patients, including targeted therapy, proton therapy and clinical trials.
Each patient’s colon cancer journey is unique, with treatment highly individualized to the patient’s specific type, stage, location and size of the cancer. The patient’s health and own wishes are also taken into account.
Moffitt Cancer Center’s approach to colon cancer
At Moffitt Cancer Center, we have experience treating all forms of colon cancer. Our team consists of many highly trained specialists, including pathologists, medical oncologists, radiation oncologists, surgeons and supportive care providers—all of whom exclusively treat patients with gastrointestinal malignancies.
Moffitt’s Gastrointestinal Oncology Program makes it possible for patients to meet with our experts in a single, convenient location. Here, patients can access some of the latest developments in treatment, including laparoscopic surgery, microsurgery, chemotherapy, targeted drug therapy, chemoembolization, vaccine therapy, brachytherapy and intensity-modulated radiation therapy (IMRT). Our patients can also participate in cutting-edge clinical trials through which they can receive novel therapies under the supervision of a skilled oncology team before those therapies are widely available in other settings.
Moffitt Cancer Center’s expert oncologists can help you learn more about the different options for colon cancer and provide you with detailed information that is specific to your precise diagnosis. To schedule an appointment, call 1-888-663-3488 or submit a new patient registration form online.