Colon cancer, which affects the large intestine, is one of the most common
cancers in the United States.
Medical experts typically group it with rectal cancer in a category called colorectal cancer.
Colon and rectal cancers generally start as abnormal growths, called colorectal polyps, in the lining of the colon or rectum.
More than 90 percent of colon and rectal cancers are a type known as adenocarcinomas.
Signs and Symptoms of Colon Cancer
Symptoms of colorectal cancer can resemble other conditions, like hemorrhoids. When in doubt, the smart decision is to speak with a doctor as soon as possible.
The most common symptoms 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 of needing to have a bowel movement that is not relieved by having one
- Rectal bleeding with bright red blood or darker stools
- Cramping or abdominal pain
- Unexplained weight loss
Causes and Risk Factors of Colon and Rectal Cancer
Researchers are still trying to fully understand the
causes of colon cancer. They do know that a small number of people develop colorectal cancer because of rare genetic mutations passed down through their families. Yet for the vast majority of patients, colorectal cancer reflects a complex interplay between genetics and lifestyle.
Doctors have identified a number of factors that increase a person’s odds of developing colorectal cancer. Risk factors that may be within a person’s power to modify include:
- Obesity or excess weight, especially around the midsection
- A physically inactive lifestyle
- A diet that includes lots of red meat (beef and lamb) and processed meat (certain lunch meats and hot dogs)
- Smoking
- Moderate to heavy alcohol use
- Type 2 diabetes
Risk factors that are not under a person’s control include:
- Age (although individuals can develop colorectal cancer at any age, people older than 50 are at highest risk)
- A personal or family history of colorectal cancer or polyps
- A personal history of inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis
- Rare inherited genetic syndromes, such as Lynch syndrome
- Being assigned male at birth
When Lynch Syndrome Runs in the Family
Sometimes an inherited gene mutation leads to an increased risk of colon cancer. When more than one close family member has been affected by colon cancer, a doctor may suggest that family members be tested for Lynch syndrome.
A person with Lynch syndrome has up to an 80 percent lifetime risk of colon cancer and up to a 60 percent chance of endometrial cancer. It also increases the risk for other cancers.
How Is Colon and Rectal Cancer Diagnosed?
Colorectal cancer is often diagnosed after a screening test identifies something suspicious. Some tests look for blood in your stool or tumor DNA in your blood. Others can spot abnormal growths in your colon or rectum. A biopsy is then used to confirm the presence of cancer cells. Additional tests determine the extent of the cancer and whether it has spread.
It’s important to get regular screenings for colorectal cancer for several reasons:
- They can detect cancer in people who have no symptoms.
- They help doctors find and remove colorectal polyps before they become cancerous.
- They can also detect this cancer early, when it’s most treatable.
Screening is recommended for everyone between ages 45 and 75 if you’re at average risk for colorectal cancer. Your doctor may recommend you start screenings earlier if you’re at higher risk. How often you need them depends on which kind of test you use, your risk level, and what your previous results were.
- Fecal Tests A sample of your stool is tested for the presence of blood or abnormal DNA. A positive result should be followed up with a colonoscopy.
- Liquid Biopsy Two tests are approved that can detect tumor DNA in your blood. A positive result should be followed up with a colonoscopy.
- Colonoscopy A long, thin tube with a light and a camera called a colonoscope is inserted into your gastrointestinal tract through your rectum and allows your doctor to view your entire colon. Doctors can remove suspicious tissue using instruments passed through the colonoscope. You’re sedated and will probably sleep through the procedure.
- Sigmoidoscopy This procedure is similar to a colonoscopy, but only extends to the lowest parts of your colon.
- Virtual Colonoscopy Also called CT colonography, this is a less invasive, but potentially less thorough, way to view your colon. A computed tomography (CT) machine takes X-rays from outside your abdomen to produce three-dimensional images of the inside of your colon and rectum.
If you’re having symptoms, or if a blood test is positive, you should see your doctor. They’ll talk to you about your symptoms and health history and give you a physical exam. They may give you a digital rectal exam, in which they insert a gloved finger into your rectum to feel for lumps.
A colonoscopy is the main tool for identifying colon cancer or precancerous polyps (and removing them). Samples of tissue removed during that procedure will be examined under a microscope to look for cancer cells. That’s called a biopsy.
Colon and Rectal Cancer Stages: What They Can Tell You
Staging colorectal cancer — describing the extent of the disease — helps doctors make treatment decisions and predict outcomes.
For colon cancer and rectal cancer, physicians review imaging scans and other tests to see whether the cancer is limited to the inner lining of the colon or rectum or has grown into the colon or rectal wall, has spread to nearby lymph nodes, or has metastasized to additional organs or sites in the body.
Tests that may be used include:
- Computed tomography (CT) scan
- Magnetic resonance imaging (MRI)
- Positron emission tomography (PET) scan
- Biopsy of lymph nodes
Physicians quantify all this information to determine a stage from 0 to 4. Generally, the lower the stage, the less advanced the disease is, and the better the prognosis.
Treatment and Medication Options for Colon and Rectal Cancer
If you have colon cancer or rectal cancer, you will likely have surgery, radiation therapy, or medication — or some combination of these
treatments.
Surgery
Surgery is often the first choice for many early-stage colon cancers and most rectal cancers. Doctors can remove diseased tissue during a colonoscopy. Or you may need to have an entire section of your colon or rectum removed.
In that case, either the remaining sections are reattached to each other or you may need a procedure called a colostomy, which creates an opening in your abdomen for stool to pass through and be collected in a bag. This situation is usually temporary.
With cancer that has spread to other organs, you may have those tumors removed during the colon surgery, or at a later time.
Radiation
Radiation therapy employs various types of radiation to destroy cancer cells. You may get this before surgery to try to shrink the tumor, or after surgery to kill any remaining cancer cells. It’s more common in treating rectal cancer than colon cancer, and in treating cancer that has spread to other parts of your body.
Medication Options
Several different kinds of drug treatments can be used for colon and rectal cancer. These are most often used for cancer that has spread throughout your body or come back after earlier treatment. Or you may get them before surgery to try to shrink the tumor, or after surgery to kill any remaining cancer cells.
Chemotherapy uses medicines that go throughout your body to kill cancer cells. Commonly used drugs include:
- Capecitabine (Xeloda)
- Fluorouracil (Adrucil)
- Irinotecan (Camptosar)
- Oxaliplatin (Eloxatin)
- Trifluridine and tipiracil (Lonsurf)
Other therapies approved by the U.S. Food and Drug Administration include encorafenib (Braftovi) in combination with fluorouracil-based chemotherapy and cetuximab (Erbitux) targeted therapy.
Targeted therapy involves drugs that attack cancer cells with unique genetic or protein targets. Tumor cells may be tested to see if one might be helpful for you. Targeted therapy drugs approved for treating stage IV colorectal cancer include:
- Adagrasib (Krazati)
- Bevacizumab (Avastin)
- Cetuximab (Erbitux)
- Encorafenib (Braftovi)
- Fruquintinib (Fruzaqla)
- Panitumumab (Vectibix)
- Ramucirumab (Cyramza)
- Regorafenib (Stivarga)
- Tucatinib (Tukysa)
- Ziv-aflibercept (Zaltrap)
Immunotherapy uses the body’s own immune system to battle cancer. Certain drugs called checkpoint inhibitors have been shown to help a small subset of patients with colorectal cancer whose tumors have specific genetic changes. The approved drugs are:
- Ipilimumab (Yervoy)
- Nivolumab (Opdivo)
- Pembrolizumab (Keytruda)
Disparities and Inequities in Colon and Rectal Cancer
Colorectal cancer is the fourth-most-common cancer among men and women in the United States, after lung, breast, and prostate cancer (and excluding skin cancers), making up about 8 percent of all new cancer cases in the country.
It’s also the second leading cause of cancer death in the United States, behind lung cancer.
In the U.S., colorectal cancer makes up 7.6 percent of all new cancer cases, according to the National Cancer Institute.
While the number of new cases among people over age 50 has been dropping, it’s been rising for people under age 50.
Native American, Alaska Native, and Black people have both greater numbers of new cases and a higher death rate compared with other races in the United States. People in these groups often face barriers to screening, according to the National Comprehensive Cancer Network.
Lifestyle Changes and Prevention of Colon and Rectal Cancer
- Quit or cut back on smoking, if you smoke.
- Maintain a healthy weight based on your height, age, and other factors.
- Exercise regularly.
- Avoid moderate to heavy alcohol use.
- Follow a healthful diet that keeps red and processed meats to a minimum.
- Get the recommended screening tests when you’re due.
- Ask your doctor about aspirin if you are part of a high-risk group — taking it daily for 5 to 10 years can be protective if benefits outweigh risks in your case.
If you’ve already had colon or rectal cancer, you’ll need follow-up screenings to look for signs of whether the cancer has returned. These include regular colonoscopies, a blood test to look for a protein shed by tumor cells called carcinoembryonic antigen, and CT scans of your chest, abdomen, and pelvis.
Complications of Colon and Rectal Cancer
Colorectal cancer can cause bleeding in your digestive tract, which can lead to anemia, or a low red blood cell count. That can make you feel tired and weak. If it goes undetected, a tumor can grow large enough to block your colon or cause a hole in the intestinal wall.
Colorectal cancer can also metastasize to other organs and tissues. When that happens, it most often affects the liver.
But it can also go to your lungs, other places in the abdomen, and other locations.
When you’ve had colon cancer, you may have changes to your bowel function, such as diarrhea or fecal incontinence.
These conditions may be temporary or permanent. Tell your doctor so they can help you manage them.
If you have a colostomy, you’ll work with a therapist who will teach you to take care of it and manage everyday activities.
Colon and Rectal Cancer Support
At some point in the process of — or after — a cancer diagnosis, you may find yourself in need of organizations that can step in and provide information, support, and help with unforeseen needs, like financial aid and words of wisdom from people who have been there. We’ve collected some of the most helpful resources for you.
BlueHQ
The Colorectal Cancer Alliance sponsors BlueHQ, an online support hub for patients and caregivers. You can get information and connect with patient navigators and other people with the disease.
Fight Colorectal Cancer
Fight Colorectal Cancer is a patient-empowerment group that advocates for policy change and raises money for research. Its website has a number of helpful resources, including a doctor finder, a way to search for clinical trials, and a list of financial assistance programs.
Faces of Blue
The Colon Cancer Coalition raises awareness and works to increase screening rates. You can share your story on its Faces of Blue platform and get inspiration from fellow survivors.
