Cancer is when cells in the body begin changing and growing out of control. These cells can form lumps of tissue called tumors. Cancer that forms in the colon is called colon cancer. Cancer that forms in the rectum is called rectal cancer. These cancers are similar, so they are sometimes just called colorectal cancer.
Understanding the colon and rectum
The colon and rectum make up the large intestine. It’s also called the large bowel. The colon is a muscular tube that forms the last part of the digestive tract. It absorbs water and stores food waste. The colon is about 5 feet long. The rectum is the last 6 inches of the large intestine. The colon and rectum have a smooth inner lining made of millions of cells. Changes in these cells can lead to growths in the colon that can become cancer.
When the colon lining changes
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 (adenoma) can change and become cancer. The longer a polyp is there and the larger a polyp grows, the more likely this is to happen. Over a period of years, polyps can become cancer. These growths should be removed when possible. Removing polyps early may prevent cancer from forming.
Colorectal cancers. These usually start when polyp cells begin growing abnormally. As a cancer tumor grows, it can invade the deeper layers of the colon or rectal wall. In time, cancer can grow beyond the colon or rectum and into nearby organs. 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 earlier a cancer tumor is removed, the better the chance of preventing its spread.
Treatment choices for colon and rectal cancer
You and your healthcare provider will discuss a treatment plan that’s best for your needs. Treatment options can include:
Surgery. This is often done to remove the cancerous parts of the colon and rectum. Some nearby tissue is removed as well. This may include nearby lymph nodes.
Chemotherapy. This may be done in addition to surgery. Or it may be done instead of surgery if the cancer has spread. This therapy uses medicines to attack cancer cells. It is known as systemic therapy. This is because it works throughout the body. It's usually done as an outpatient procedure in a healthcare provider's office, clinic, or hospital. You may take the medicine in pill form. Or you may have it through an IV line or infusion pump. This is a device that slowly releases medicine into your bloodstream.
Radiation therapy. This may be used for rectal cancer. This treatment uses high-energy X-rays to kill cancer cells. It’s known as localized therapy. This is because it targets the specific area of the body affected by the cancer. It is usually done on an outpatient basis in a hospital or radiation clinic.
Targeted therapy. This uses medicines that target proteins or cell functions that help cancer cells grow. Some of these medicines are given along with chemotherapy medicines. Other medicines are used by themselves.
Immunotherapy. This treatment uses medicines that help the body's immune system attack the cancer. These medicines can be helpful in a small percentage of colorectal cancers that have certain gene changes. Immunotherapy might be an option for advanced colorectal cancers with these changes. It may be used after chemotherapy has not worked.