What Is Colon and Rectal Cancer (Colorectal Cancer)? Cancer occurs when cells in the body begin changing and multiplying 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 also called colorectal cancer.
Understanding the colon and what causes colorectal cancer
The colon (also called the large intestine or large bowel) is a muscular tube that forms the last part of the digestive tract. It absorbs water and stores food waste. The colon is about 4 to 6 feet long. The rectum is the last 6 inches of the colon. The colon and rectum have a smooth lining composed of millions of cells. Changes in these cells can lead to growths in the colon that can become cancerous and should be removed.
Changes that occur in the cells that line the colon or rectum can lead to growths called polyps. Over a period of years, polyps can turn cancerous. Removing polyps early may prevent cancer from ever forming.
- Polyps are fleshy clumps of tissue that form on the lining of the colon or rectum. Small polyps are usually benign (not cancerous). However, over time, cells in a polyp can change and become cancerous. The larger a polyp grows, the more likely this is to happen. Also, certain types of polyps known as adenomatous polyps are considered premalignant. This means that they will almost always become cancerous if they’re not removed.
- Colorectal cancers usually start when polyp cells begin growing abnormally. As a cancerous tumor grows, it may involve more and more of the colon or rectum. In time, cancer can also grow beyond the colon or rectum and spread to nearby organs or to glands called lymph nodes. The cells can also travel to other parts of the body. This is known as metastasis. The earlier a cancerous tumor is removed, the better the chance of preventing its spread.
Symptoms and Signs of Colon Cancer
People with colorectal cancer often do not have symptoms right away. By the time symptoms occur, 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.
Colon cancer 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 mucous on them
- Ongoing gas pains, bloating, fullness, or cramps
- Unexplained weight loss
Types of Colon Cancer Treatment
You and your healthcare provider will discuss a treatment plan that's best for your needs. Different combinations of treatment may be used, depending on the stage of the cancer and other factors. Each treatment has its own goals. Here is 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 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 the medicines are given in a way that lets them enter the bloodstream, they treat cancer cells throughout the body. That way they can treat cancer that has spread. This type of treatment is called systemic. Medicines can also be given to attack cancer cells in specific organs, such as the liver. This treatment is called local. Chemotherapy might also be used before surgery to shrink tumors. When used before surgery, it is called neoadjuvant therapy. It might be used after surgery to kill or control any remaining cancer cells. When used after surgery, it is called an 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 treatment 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 is called adjuvant radiation therapy. Then the goal is to reduce the chance that the cancer will come back.
- Targeted therapy. This type of therapy uses medicines that target proteins or cell functions that help cancer cells grow. Some of these medicines are given along with chemotherapy medicines, while others are used by themselves. The goal is to prevent the cancer from growing. It may also be used to help chemotherapy get inside the tumor. This can help it be more effective.
- Immunotherapy. The goal of this type of treatment is to help the body's own immune system attack 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 an option 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 deliver chemotherapy or radiation directly to the tumor.
- Supportive care. Your healthcare provider may advise therapies that help ease your symptoms, but don’t treat the cancer. These can sometimes be used along with other treatments. Or your healthcare provider may suggest supportive care if he or she believes that available treatments are more likely to do you more harm than good.