Cancer starts when cells change (mutate) and grow out of control. The changed (abnormal) cells often grow to form a lump or mass called a tumor. Cancer cells can also grow into (invade) nearby areas. They can spread to other parts of the body, too. This is called metastasis.

Colorectal cancer is cancer that starts in either your colon or your rectum. These make up the lower part of your digestive or gastrointestinal (GI) tract. Both types of cancer have a lot in common. So they're often called colorectal cancer.

The colon and rectum make up the large intestine. This is sometimes called the large bowel. The colon is a muscular tube about 5 feet long. It forms the last part of the digestive tract. It absorbs water from the remaining food matter. The rectum is the last 6 inches at the end of the digestive tract. It acts as a storage space before waste (feces or stool) leaves the body through the anus. The colon and rectum are made up of many layers. Both have a wet inner lining made of millions of cells.

Changes in the cells that line the inside of the colon or rectum can lead to growths called polyps. Over time, some types of polyps can become cancer. The type of polyp that most often develops into cancer is called an adenoma or an adenomatous polyp. Adenocarcinoma is the name of the cancer that starts in these polyps. They're the most common type of colorectal tumor. Removing polyps early (when they're small) may stop cancer from ever forming.

A risk factor is anything that may increase your chance of having a disease. The exact cause of someone's cancer may not be known. But risk factors can make it more likely for a person to have cancer. Some risk factors may not be in your control. But others may be things you can change.

You have a higher risk for colorectal cancer if you:

• Are older.
• Are Black or Ashkenazi Jewish.
• Are male.
• Have a history of colorectal polyps.
• Have a history of colon, rectum, or ovarian cancer.
• Have ulcerative colitis or Crohn's disease.
• Have a family history of colon or rectum cancer.
• Have certain inherited syndromes, such as Lynch syndrome (HNPCC) or familial adenomatous polyposis (FAP).
• Have obesity.
• Are not active.
• Eat a diet high in red meats and processed meats.
• Drink a lot of alcohol.
• Have type 2 diabetes.
• Smoke.

Talk with your doctor about your risk factors for colorectal cancer and what you can do about them.

There's no sure way to prevent colorectal cancer. But you can make changes that can help you control some of the risks. Having a healthy lifestyle may help to lower your risk for colorectal cancer. This includes:

• Being physically active.
• Eating lots of fruits, vegetables, and whole grains.
• Limiting red and processed meats.
• Staying at a healthy weight.
• Not smoking or drinking alcohol.
• Getting enough calcium and vitamin D.
• Thinking about taking low-dose aspirin if you also have heart disease.
• Talking with your doctor about screening for colorectal polyps and cancer.
• Discussing menopausal hormone use with your doctor.

Talk with your doctor about what you can do to help prevent colorectal cancer.

Colorectal cancer may be found with a screening test. Screening means checking for a health problem before a person has symptoms. It may find some types of cancer early, when they're small, haven't spread, and are often easier to treat.

The screening tests to find polyps or colorectal cancer or both are:

• Colonoscopy
• Flexible sigmoidoscopy
• Virtual colonoscopy (CT colonography)
• Fecal occult blood test (FOBT) or fecal immunochemical test (FIT)
• Stool DNA test
• Blood test

Experts say screening should start at age 45 for people who are at average risk for colorectal cancer. Screening may be advised earlier if you are at higher risk. Talk with your doctor about screening to make the choice that's best for you.

People with colorectal cancer seldom have symptoms right away. By the time symptoms start, the cancer may have grown or spread to other organs. This can make it harder to treat. That's why routine colorectal cancer screening is important. Symptoms can include:

• A change in bowel habits that lasts for more than a few days, such as diarrhea, constipation, or a feeling that your bowel is not empty after a bowel movement.
• Bright red or very dark blood in your stool.
• Constant tiredness.
• Stools that are thinner than usual.
• Stools that look slimy or have mucus on them.
• Ongoing gas pains, bloating, fullness, or cramps.
• Unexplained weight loss.
• Vomiting.

Many of these may be caused by other health problems. Still, it's important to see your doctor if you have these symptoms. Only a doctor can tell if you have cancer.

If your doctor thinks you may have colorectal cancer, exams and tests will be needed to know for sure. Your doctor will ask you about your health history, your symptoms, risk factors, and family history of disease. A physical exam will be done.

A biopsy is the only way to be sure of a colorectal cancer diagnosis. The most common type of biopsy is an endoscopic biopsy. This is usually done during a colonoscopy. A small sample of the changed tissue is taken out and checked for cancer cells. It usually takes several days for the results of your biopsy to come back.

After a diagnosis of colorectal cancer, you'll need more tests. These help your doctors learn more about your overall health and the cancer. They're used to find out the stage of the cancer. The stage is how much cancer there is and how far it has spread (metastasized) in your body. It's one of the most important things to know when deciding how to treat the cancer.

Once your cancer is staged, your doctor will talk with you about what the stage means for your treatment. Be sure to ask your doctor to explain the details of your cancer to you in a way you can understand.

Your treatment choices depend on the type of colorectal cancer you have, test results, and the stage of the cancer. The goal of treatment may be to cure you, control the cancer, or help ease problems caused by the cancer. Talk with your health care team about your treatment choices, the goals of treatment, and possible risks and side effects. Other things to think about are if the cancer can be removed with surgery, how your body will look and work after treatment, and your overall health.

Types of treatment for cancer are either local or systemic. Local treatments remove, destroy, or control cancer cells in one area. Surgery and radiation are local treatments. Systemic treatment is used to destroy or control cancer cells that may have traveled around your body. When taken by pill or injection, chemotherapy and targeted therapy are systemic treatments. You may have just one treatment or a combination of treatments. Tests will be done during treatment to see how well it's working.

Types of treatment for colorectal cancer include:

• Surgery.
• Chemotherapy.
• Radiation therapy.
• Targeted therapy.
• Immunotherapy.
• Ablation and embolization.
• Supportive care to ease symptoms of treatment or the cancer.

Researchers are always looking for new ways to treat cancer. These new methods are tested in clinical trials. Talk with your doctor to find out if there are any clinical trials you should think about.

Talk with your health care providers about your treatment options. Make a list of questions. Think about the benefits and possible side effects of each option. Talk about your concerns with your doctor before making a decision.

Cancer treatments, like chemotherapy and radiation, can damage normal cells. This can cause side effects like hair loss, mouth sores, and vomiting. Talk with your doctor about side effects linked with your treatment. There are often ways to manage them. There may be things you can do and medicines you can take to help prevent or control many treatment side effects.

Colorectal cancer and its treatment may permanently change the way you pass stool from your body. It happens when surgery is done to take out the colon with cancer and create a colostomy. This is a new opening (stoma) on your belly. It's covered with a pouch that sticks to your skin and collects stool. Ask your doctor if you will have a temporary or permanent colostomy as a result of your treatment.

Many people feel worried, depressed, and stressed when dealing with cancer. Getting treatment for cancer can be hard on your mind and body. Keep talking with your health care team about any problems or concerns you have. Work together to ease the effect of cancer and its symptoms on your daily life.

Here are some tips:

• Talk with your family or friends.
• Ask your health care team or social worker for help.
• Speak with a counselor.
• Talk with a spiritual advisor, such as a minister or rabbi.
• Ask your health care team about medicines for depression or anxiety.
• Keep socially active.
• Join a cancer support group in person or online.

Cancer treatment is also hard on the body. To help yourself stay healthier, try to:

• Eat a healthy diet, with a focus on high-protein foods.
• Drink plenty of water, fruit juices, and other liquids.
• Keep physically active.
• Rest as much as needed.
• Talk with your health care team about ways to manage treatment side effects.
• Take your medicines as directed by your team.

Your doctor may tell you to contact them if you have any of the below:

• New symptoms or symptoms that get worse
• Signs of an infection, such as a fever
• Side effects of treatment that affect your daily function or don't get better with treatment

Ask your doctor what symptoms to watch for and when to contact them. Know how to get help after office hours and on weekends and holidays.

• Colorectal cancer most often starts in the inner lining of the colon or rectum. These organs make up the end of the gastrointestinal (GI) tract or digestive system.
• Screening tests can be used to help look for colorectal cancers before they cause symptoms. This is important because symptoms may not start until the tumor is big or has spread.
• Symptoms can include changes in your bowel movements, blood in your stool, belly pain or cramps, unplanned weight loss, and extreme tiredness.
• Colonoscopy, blood tests, and a biopsy are usually needed to diagnose colorectal cancer.
• Treatment can include surgery, radiation, chemotherapy, targeted therapy, and immunotherapy. Many times, more than one type of treatment is used.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when they should be reported.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours and on weekends and holidays.