What Is Colon and Rectal Cancer? Symptoms, Causes, Diagnosis, Treatment, and Prevention
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.
The colon and rectum are part of the digestive system. The colon is about five feet long and accounts for most of the large intestine. The rectum makes up the final six inches of the large intestine and is considered the passageway between the colon and the anus.
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. These begin in glandular (secretory) cells which line the colon and rectum and produce mucus to lubricate the intestinal tract.
Colorectal cancer can be challenging to detect early because it may not cause symptoms until it is more advanced. When symptoms do occur, they can be easy to blame on something else — hemorrhoids, for instance, or irritable bowel syndrome.
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
Researchers are still trying to fully understand the causes. 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
African American, Native American, Alaska Native, or Eastern European Jewish heritage
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 cancer of the stomach, ovaries, small bowel, brain, urinary tract, hepatobiliary tract (liver, bile ducts, and gallbladder), and sebaceous glands.
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. (It typically takes about 10 years for new polyps to turn into cancer.)
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.
Screening tests include:
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. 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 further 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
X-ray
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.
If colorectal cancer is found at the local stage, before it spreads beyond the colon or rectum, the five-year survival rate is above 90 percent. Unfortunately, only a little more than one-third of all colon cancers and rectal cancers are found this early, in large part because of inadequate screening. Colorectal cancer found after it has spread to distant parts of your body has a five-year survival rate of less than 16 percent.
Colon and rectal cancer can come back after treatment, and you can also develop another cancerous polyp. One study published in 2023 found that almost 16 percent of people treated for colorectal cancer had a recurrence within five years. That highlights the importance of follow-up screening.
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)
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 colorectal cancer patients whose tumors have specific genetic changes. The approved drugs are:
While it isn’t always possible to prevent colorectal cancer, there are a number of things you can do to lower your risk.
Don’t smoke. Although people associate cigarettes with lung cancer, they’re less aware of the strong connection between smoking and colorectal cancer.
Maintain a healthy weight.
Exercise regularly.
Avoid moderate to heavy alcohol use.
Follow a healthy diet that keeps red and processed meats to a minimum.
Get the recommended screening tests when you’re due.
Ask your doctor about aspirin. Taking it daily for 5 to 10 years can be protective.
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 (CEA), and CT scans of your chest, abdomen, and pelvis.
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, brain, abdomen, and other locations. That can cause other complications including jaundice, breathing problems, and headaches.
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.
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.
Around 1 in 25 Americans will develop colon cancer or rectal cancer at some point in their lives, according to the most recent data (2018–2021) from the National Cancer Institute, with some 152,000 new cases estimated for 2024.
While the number of new cases among people over age 50 has been dropping, it’s been rising for people under age 50.
Compared to other races, Native American, Alaska Native, and Black people have both greater numbers of new cases and a higher death rate.
Having certain other medical conditions puts you at higher risk of developing colorectal cancer. These include:
Inflammatory bowel disease This includes both Crohn’s disease and ulcerative colitis. If you’ve been living with either of these for eight years or more, you should have a colonoscopy at least every two years.
Type 2 diabetes The two diseases share common risk factors, and researchers think high levels of insulin and glucose in the blood of people with type 2 diabetes may encourage colon cancer cells to grow.
Obesity Research indicates rising obesity rates could be contributing to an increase in colorectal cancer in younger people.
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.
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 is a patient-empowerment group that advocates for policy change and raises money for research. Their 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.
The Colon Cancer Coalition raises awareness and works to increase screening rates. You can share your story on their Faces of Blue platform and get inspiration from fellow survivors.
Colorectal cancer usually begins as abnormal growths called polyps inside your large intestine. Smoking, being overweight, and being physically inactive are among the things that increase your risk. One of the most effective ways to prevent this disease is with regular screenings to locate and remove polyps before they become cancerous.
