The rectum and the colon make up the large intestine, or large bowel. The rectum is the last six inches of the large bowel and connects the colon to the anus. Cancer of the rectum and/or colon is referred to as colorectal cancer and is the fourth most common cancer in the United States. The two cancers are grouped together because they share many characteristics and are treated similarly. About one-third of the 145,000 cases of colorectal cancers diagnosed each year are found in the rectum.
Rectal cancer occurs when cells in the rectum mutate and grow out of control. The disease may also develop when growths, called polyps, on the inner wall of the rectum develop and become cancerous.
The risk of rectal cancer increases with age. The average age of a person diagnosed with colorectal cancer is 68. Men have a higher risk than women. The risk of rectal cancer may be reduced, and the disease may be prevented or caught early, with regular examinations and lifestyle changes, such as:
Worldwide, colorectal cancer is the second most common cancer in females and the third most common cancer in males.
Rectal cancer occurs when healthy cells in the rectum develop errors in their DNA. In most cases, the cause of these errors is unknown.
Healthy cells grow and divide in an orderly way to keep your body functioning normally. But when a cell’s DNA is damaged and becomes cancerous, cells continue to divide even when new cells aren’t needed. As the cells accumulate, they form a tumor.
With time, the cancer cells can grow to invade and destroy normal tissue nearby. And cancerous cells can travel to other parts of the body.
In some families, gene mutations passed from parents to children increase the risk of colorectal cancer. These mutations are involved in only a small percentage of rectal cancers. Some genes linked to rectal cancer increase an individual’s risk of developing the disease, but they don’t make it inevitable.
Two well-defined genetic colorectal cancer syndromes are:
FAP, HNPCC and other, rarer inherited colorectal cancer syndromes can be detected through genetic testing. If you’re concerned about your family’s history of colon cancer, talk to your doctor about whether your family history suggests you have a risk of these conditions.
The characteristics and lifestyle factors that increase your risk of rectal cancer are the same as those that increase your risk of colon cancer. They include:
Tests used to diagnose rectal cancer include the following:
After rectal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the rectum or to other parts of the body.
The process used to find out whether cancer has spread within the rectum or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.
The following tests and procedures may be used in the staging process:
There are three ways that cancer spreads in the body.
Cancer can spread through tissue, the lymph system, and the blood:
Cancer may spread from where it began to other parts of the body.
When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.
The metastatic tumor is the same type of cancer as the primary tumor. For example, if rectal cancer spreads to the lung, the cancer cells in the lung are actually rectal cancer cells. The disease is metastatic rectal cancer, not lung cancer.
In stage 0 rectal cancer, abnormal cells are found in the mucosa (innermost layer) of the rectum wall. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.
In stage I rectal cancer, cancer has formed in the mucosa (innermost layer) of the rectum wall and has spread to the submucosa (layer of tissue next to the mucosa) or to the muscle layer of the rectum wall.
Stage II rectal cancer is divided into stages IIA, IIB, and IIC.
Stage III rectal cancer is divided into stages IIIA, IIIB, and IIIC.
In stage IIIA, cancer has spread:
In stage IIIB, cancer has spread:
In stage IIIC, cancer has spread:
Stage IV rectal cancer is divided into stages IVA, IVB, and IVC.
Different types of treatment are available for patients with rectal cancer. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials. A treatment clinical trial is a research study meant to help improve current treatments or obtain information on new treatments for patients with cancer. When clinical trials show that a new treatment is better than the standard treatment, the new treatment may become the standard treatment. Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Surgery is the most common treatment for all stages of rectal cancer. The cancer is removed using one of the following types of surgery:
After the cancer is removed, the surgeon will either:
Radiation therapy and/or chemotherapy may be given before surgery to shrink the tumor, make it easier to remove the cancer, and help with bowel control after surgery. Treatment given before surgery is called neoadjuvant therapy. After all the cancer that can be seen at the time of the surgery is removed, some patients may be given radiation therapy and/or chemotherapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called adjuvant therapy.
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy:
The way the radiation therapy is given depends on the type and stage of the cancer being treated. External radiation therapy is used to treat rectal cancer.
Short-course preoperative radiation therapy is used in some types of rectal cancer. This treatment uses fewer and lower doses of radiation than standard treatment, followed by surgery several days after the last dose.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly in the cerebrospinal fluid, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy).
Chemoembolization of the hepatic artery is a type of regional chemotherapy that may be used to treat cancer that has spread to the liver. This is done by blocking the hepatic artery (the main artery that supplies blood to the liver) and injecting anticancer drugs between the blockage and the liver. The liver’s arteries then carry the drugs into the liver. Only a small amount of the drug reaches other parts of the body. The blockage may be temporary or permanent, depending on what is used to block the artery. The liver continues to receive some blood from the hepatic portal vein, which carries blood from the stomach and intestine.
The way the chemotherapy is given depends on the type and stage of the cancer being treated.
See Drugs Approved for Colon and Rectal Cancer for more information.
Active surveillance is closely following a patient’s condition without giving any treatment unless there are changes in test results. It is used to find early signs that the condition is getting worse. In active surveillance, patients are given certain exams and tests to check if the cancer is growing. When the cancer begins to grow, treatment is given to cure the cancer. Tests include the following:
Targeted therapy is a type of treatment that uses drugs or other substances to identify and attack specific cancer cells without harming normal cells.
Types of targeted therapies used in the treatment of rectal cancer include the following:
There are different types of monoclonal antibody therapy:
Immunotherapy is a treatment that uses the patient’s immune system to fight cancer. Substances made by the body or made in a laboratory are used to boost, direct, or restore the body’s natural defenses against cancer. This type of cancer treatment is also called biotherapy or biologic therapy.
Immune checkpoint inhibitor therapy is a type of immunotherapy:
Stage 0 (Carcinoma in Situ)
Treatment of stage 0 may include the following:
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done.
Treatment of stage I rectal cancer may include the following:
Use our clinical trial search to find NCI-supported cancer clinical trials that are accepting patients. You can search for trials based on the type of cancer, the age of the patient, and where the trials are being done.
Treatment of stage II and stage III rectal cancer may include the following:
Stage IV and recurrent rectal cancer treatment
Treatment of stage IV and recurrent rectal cancer may include the following:
Treatment of rectal cancer that has spread to other organs depends on where the cancer has spread.
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