The colon and rectum make up the large intestine (also called the large bowel). The colon is a muscular tube that's about 5 feet long. It forms the last part of the digestive tract. It absorbs water and stores food waste. The rectum is the last 6 inches of the large intestine.

The colon and rectum have a smooth inner lining. It is made of millions of cells. These cells replace themselves every day to keep the lining healthy. Changes in these cells can lead to growths in the colon and rectum that can become cancer.

Changes that happen in the cells that line the colon or rectum include:

• Polyps. These are fleshy clumps of tissue that form on the inner lining of the colon or rectum. Small polyps are usually benign (not cancer). But over time, cells in a type of polyp known as an adenomatous polyp (or adenoma) can change and become cancer. The longer a polyp is there and the larger a polyp grows, the more likely it is to become cancer. This happens over a period of years. That's why these growths should be removed when possible. Removing polyps early may prevent cancer from forming. 

• Colorectal cancers. These usually start when polyp cells grow out of control. As cancer grows, it can invade the deeper layers of the colon or rectal wall. Cancer can grow beyond the colon or rectum and into nearby organs as time goes on. It can spread to nearby lymph nodes. The cancer cells can also travel to other parts of the body. This is known as metastasis. The sooner a cancer tumor is removed, the better the chance of keeping it from spreading.

You and your healthcare provider will decide on the treatment plan that’s best for your needs. Treatment choices can include:

• Surgery. This is the most common treatment. It's done to remove the cancer in the colon and rectum. Some nearby tissue is also removed. This may include nearby lymph nodes.

• Chemotherapy. This treatment may be done along with surgery. Or it may be done instead of surgery if the cancer has spread. Strong medicines are used to kill cancer cells. This is called systemic therapy. It works throughout the body. Chemotherapy is often done as an outpatient procedure in a healthcare provider's office. It is also done at a clinic or hospital. You may take the medicine as a pill. Or you may get it through an intravenous (IV) infusion. This slowly releases the medicine into your blood.

• Radiation therapy. This treatment may be used for rectal cancer. High-energy X-rays are focused on the tumor to kill cancer cells. It’s known as localized therapy. It targets the cancer and not the whole body. It's usually done on an outpatient basis in a hospital or radiation clinic.

• Targeted therapy. This treatment uses medicines that target certain genes, proteins, or cell functions that help cancer cells grow. Cancer cells are tested to see if they have the changes the medicines target. Sometimes targeted therapy is given along with chemotherapy. It can also be used by itself.

• Immunotherapy. This treatment uses medicines that help the body's immune system attack the cancer. These medicines can be helpful in treating colorectal cancers that have certain gene changes. Immunotherapy might be a choice for advanced colorectal cancers with these changes. It may also be used if chemotherapy hasn't worked. 

You may have questions and concerns about your treatment choices. You may also want to know how you’ll feel and function after treatment, and if you’ll have to change your normal activities.

Your healthcare provider is the best person to answer your questions. They can tell you what your treatment choices are, how well they’re expected to work, and what the risks and side effects are. Your healthcare provider may advise a specific treatment. Or you may be presented more than one potential treatment course and be asked to offer your opinion on the best choice for you. It can be hard to make this decision. It's important to take the time you need to make the best decision.

Deciding on the best plan may take some time. Talk with your healthcare provider about how much time you can take to explore your choices. You may want to get another opinion before deciding on your treatment plan. You may also want to involve your family and friends in this process.

For many colorectal cancers, the goal of treatment is to cure the cancer. If cure isn't possible, treatment may be used to shrink the cancer or keep it under control for as long as possible. Treatment can also improve your quality of life by helping control the symptoms of the disease. The goals of colorectal cancer treatment can include:

• Remove the cancer in the colon or rectum

• Remove or destroy tumors in other parts of the body

• Kill or stop the growth or spread of colorectal cancer cells

• Prevent or delay the cancer's return

• Ease symptoms caused by the cancer, like pain or eating problems caused by pressure on organs

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:

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

At first, thinking about treatment choices may seem overwhelming. Talk with your healthcare providers, nurses, and loved ones. Make a list of questions. Think about the benefits and possible side effects of each choice. Talk with your healthcare provider about any questions or concerns before making a decision.