What is colon and rectal cancer?

Colorectal cancer is cancer that starts in either your colon or your rectum. These make up the lower part of your digestive tract.

In most cases, cancer doesn't start in both places. But colon and rectal cancer have a lot in common. So, they're often called colorectal cancer.

The colon is a muscular tube about five feet long. It forms the last part of the digestive tract. It absorbs water from the remaining food matter.

The rectum is the last six inches of the digestive tract. It's the storage space for feces before it leaves the body through the anus.

Together, the colon and rectum make up the large intestine. This is sometimes called the large bowel. The colon and rectum have an inner lining made of millions of cells. Changes in these cells can lead to growths (polyps) that can become cancer.

Overview

What are the types of colon and rectal cancer?

These are the types of cancer that can start in the colon and rectum:

• Adenocarcinoma. Nearly all colorectal cancers are adenocarcinoma. This cancer starts in the lining of internal organs. The tumors start in gland cells that release or secrete fluids.
• Gastrointestinal stromal tumor. These tumors start in special cells in the wall of the digestive tract. They may be found anywhere in the digestive tract. But they rarely start in the colon. They may be benign or not cancer at first. But, over time, many do turn into cancer.
• Lymphoma. Cancer starts in a type of immune cell called a lymphocyte. Lymphomas often start in bean-sized groups of lymphocytes called lymph nodes. But they can also start in the colon, rectum or other organs.
• Carcinoid. This cancer starts in certain cells in the intestine that make hormones.
• Sarcoma. These tumors start in blood vessels, muscles or connective tissue in the colon and rectum wall.

How colorectal cancer starts and grows

Most colorectal cancers start as polyps. These are growths caused by changes in the cells that line the inside of the colon or rectum. Over time, some types of polyps can become cancer. Finding and removing polyps while they're small may stop cancer from ever forming.

Polyps are fleshy clumps of tissue that form on the inner lining of the colon or rectum. Small polyps are seldom cancer. But over time, the cells in a type of polyp called an adenomatous polyp, or adenoma, can change and become cancer. The longer a polyp is there and the bigger it gets, the more likely this will happen.

Colorectal cancers most often start when cells in a polyp start growing abnormally. As a cancer tumor grows, it can invade the outermost layers of the colon or rectal wall. Over time, the cancer can grow beyond the colon or rectum and into nearby organs. Or it can spread to nearby lymph nodes.

The cancer cells can also travel to other parts of the body, forming new tumors. This is known as metastasis. If colorectal cancer spreads, it most often goes to the liver first. But it can also spread to other organs, like the lining of the belly (peritoneum) and the lungs.

Symptoms

What are the signs of colorectal cancer?

People with colorectal cancer often don't 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. This is why routine colorectal cancer screening is important. Screening is designed to help find and even remove precancerous polyps before they become cancer.

Symptoms of colorectal cancer can include:

• A change in bowel habits that last more than a few days. (diarrhea, constipation, or a feeling that your bowel is not emptying)
• Bright red or very dark blood in your stool
• Constant tiredness
• Stools that are thinner than normal, described as "pencil thin"
• Ongoing gas pains, bloating, fullness, or cramps
• Unexplained weight loss
• Weakness

Risk Factors

What are the colorectal cancer risk factors?

Anyone can get cancer. But some factors can increase your risk of developing colorectal cancer. Some of these increase your risk by a lot, and some by only a little:

• Age. Most people who have this cancer are over age 50. But it can occur at any age.
• Race and ethnicity. Black people have the highest risk for colorectal cancer in the U.S. Jews whose families are from Eastern Europe (Ashkenazi Jews) have one of the highest colorectal cancer risks of any ethnic group in the world.
• Gender. Men have a slightly higher risk for this cancer than women.
• History of colorectal polyps. Polyps are growths in your colon and rectum. They are common in adults over age 50. They're often not cancer (benign). But over time, some polyps can become cancer. If you have had polyps called adenomas taken out of your colon in the past, you have an increased risk.
• History of colorectal cancer and some other cancers. People with colorectal cancer have an increased risk of getting it again. People with a history of cancer of the uterus or ovaries also have a higher risk.
• Ulcerative colitis or Crohn's disease. People with an inflamed colon lining (inflammatory bowel disease) caused by one of these conditions have a greater risk.
• Family history. People are at higher risk if they have a family history of colorectal cancer or polyps in a first-degree relative. This may be a parent, sibling, or child. The risk is greater if the relative was diagnosed before age 50. The risk is also greater if more than one relative is diagnosed. Still, most people with colorectal cancer don’t have a family history.
• Certain inherited syndromes. People with certain syndromes have a very high risk of colorectal disease. This includes familial adenomatous polyposis and Lynch syndrome (hereditary nonpolyposis colon cancer).
• Obesity. Colorectal cancer is more common in people who are overweight or obese than people who are not. This is even more true for men.
• Not being active. People who are not active are at increased risk for the disease.
• Diet. Colorectal cancer is linked to a diet high in red meat. This includes beef, pork, lamb and veal. It's also linked to a diet high in processed meats, such as hot dogs and lunch meats.
• Drinking a lot of alcohol. Limit yourself to no more than one drink per day for women or two drinks per day for men.
• Type 2 diabetes. People with Type 2 diabetes are more likely to get colorectal cancer.
• Smoking. Smoking raises a person's risk.

Prevention

What causes colon cancer?

Studies suggest that eating habits and obesity play a role. Choosing a healthy diet and managing your weight may help if you're a young adult. If you’re in the 50-plus group, the same tactics complement regular screening. Either way, it pays to take action.

How to prevent colon cancer

Colorectal cancer is a tale of two age groups. Although the disease is still more common in people older than 50, rates have been falling for this population. Credit increased screening – which can prevent some cases by finding precancerous growths – as one reason for this decline. But colorectal cancer rates have risen among those younger than 50 since the early ’90s.

Eating lots of red meat has been linked to an increased risk of colorectal cancer. Meanwhile, diets rich in vegetables, fruits and whole grains might decrease the risk.

You can fine-tune your menu in other ways that may help lower your risk for colorectal cancer:

• Limit your intake of processed meats
• Avoid drinking alcohol in excess
• Physical activity – Balance the calories you get from food with the ones you burn through regular exercise. An inactive lifestyle and obesity are risk factors for colorectal cancer.
• Have a screening test – Getting screened periodically for this disease is crucial. Screening helps detect cancer early when it’s easier to treat. Some tests also help find precancerous growths, called polyps, so they can be removed before they become cancerous.

Diagnosis

How is colon and rectal cancer diagnosed?

Your health care provider might believe you have colorectal cancer based on the results of a routine screening test. Or you might have symptoms that could be caused by colorectal cancer. You will need certain exams and tests to be sure. The process starts with your healthcare provider asking you questions. You'll be asked about your:

• Health history
• Symptoms
• Risk factors
• Family history of disease

Your health care provider will also do a physical exam. This will include pressing on your belly. You may also have a digital rectal exam (DRE). For a DRE, the provider puts a gloved, lubricated finger in your rectum to feel for lumps or tumors. They may feel for lymph nodes. Blood and stool tests may be done as well.

What tests might I need?

Depending on the location of your cancer, tests may include:

• Colonoscopy. This test uses a longer flexible tube that can see the anus, rectum, and entire colon.
• Proctoscopy. This test is done using a longer lighted tool (a proctoscope) to look at the inside of your anus and rectum. 
• Biopsy. A biopsy is the removal of cells or tissue for testing. It can show if the removed tissue has cancer cells in it. For colorectal cancer, a biopsy is the only way to be sure of the diagnosis. The most common type of biopsy is an endoscopic biopsy. It's often done during a colonoscopy. (Other types of biopsies include a needle biopsy and a surgical biopsy. But these are not often used to diagnose colorectal cancer.)
• CT Scan. For this test, you lie on a narrow table that moves through a ring-like CT scanner. It takes many X-rays as you slide through. A computer combines these images to make detailed pictures of your insides.
• MRI. MRIs use radio waves and magnets to make detailed pictures that look like slices of the body. You lie on a narrow table that slides through the long, narrow, tube-like scanner. Some people have trouble with this test because they don't like being in tight spaces. Let your healthcare provider know if this is a problem for you.

Treatment

How is colorectal cancer treated?

Many types of treatment can be used for colorectal cancer. Different combinations of treatment may be used, depending on the stage of the cancer and other factors. Each treatment has its own goals. Here's an overview of each type of treatment:

• Surgery. This is the most common treatment for most early stages of colon and rectal cancer. The goal of surgery is to remove the entire tumor and any cancer cells that may have spread to nearby tissue. Depending on the stage of the cancer, surgery may be all that's needed. Or surgery may come before or after another treatment is used.
• Chemotherapy. The goal of chemotherapy (chemo) is to stop cancer from growing or spreading. It does this by using medicines to either kill the cells or stop them from dividing. If chemo is given in a way that puts the medicines into the bloodstream, it treats cancer cells throughout the body. This way chemo can treat cancer that has spread. This is called systemic treatment. Chemo can also be given to attack cancer cells in certain organs, such as the liver. This is called local treatment. Chemo might also be used before surgery to shrink tumors. When used before surgery, it's called neoadjuvant therapy. It might be used after surgery to kill or control any remaining cancer cells. When used after surgery, it's called adjuvant therapy.
• Radiation therapy. The goal of radiation therapy is to kill cancer cells using high-energy X-rays. It has a major role in treating rectal cancers, but it may be used in some colon cancers as well. Like chemotherapy, it may be used before surgery to shrink tumors. This is called neoadjuvant radiation therapy. This may lower the chance that a person will need a permanent colostomy. When it's used after surgery, it's called adjuvant radiation therapy. Then the goal is to reduce the chance that the cancer will come back.
• Targeted therapy. This treatment uses medicines that target proteins or cell functions that help cancer cells grow. Some of these medicines are given along with chemotherapy, while others are used by themselves. The goal is to keep the cancer from growing. It may also be used to help chemo get inside the tumor. This can help it work better.
• Immunotherapy. The goal of this treatment is to help the body's own immune system kill the cancer cells. Medicines called checkpoint inhibitors can be used to treat some advanced colorectal cancers in which the cells have certain gene changes. This treatment might be a choice for some people who have already had chemotherapy.
• Ablation and embolization. These methods can be used to treat tumors that have spread to other parts of the body, such as the liver or lungs. Ablation is the use of heat, cold, or other methods to destroy tumors rather than removing them. For embolization, a substance is injected into a blood vessel to try to cut off a tumor's blood supply or to send chemotherapy or radiation right to the tumor.
• Stenting. If the cancer is blocking your colon, your healthcare team may recommend a stent. A stent is a hollow mesh tube. It helps keep your colon open so gas and stool can pass. This may help improve symptoms. A stent may be used as part of supportive care or before a larger surgery.
• Supportive care. Your health care provider may advise therapies that help ease your symptoms, but don’t treat the cancer. These are used along with other treatments. For example, supportive care can be medicines to prevent nausea or control pain.

At first, thinking about treatment choices may seem overwhelming. Talk with your health care providers, nurses and loved ones. Make a list of questions.

Think about the benefits and possible side effects of each choice. Talk with your care team about any questions or concerns before deciding.

Is colon cancer curable?

Yes. Survivability largely depends on the stage of colorectal cancer. The American Cancer Society reports a five-year survival rate for colon cancer that hasn’t spread and remained localized at 91%. If the cancer has spread outside the immediate region, the survival rate is 72%.