Rectal Cancer

What is rectal cancer?
Rectal cancer forms inside a portion of the large intestine, which is roughly five and a half feet long. The first five feet of the large intestine is called the colon. The colon absorbs water from stool. The rectum makes up the last six inches of the large intestine. The rectum is where the body stores stool until you have a bowel movement. Cancers found in the two organs are often grouped together as colorectal cancer.

Rectal cancer often develops slowly over several years. It typically starts as a small abnormal growth on the inner lining of the rectum. This is called a polyp. Some polyps can eventually grow into cancer.

Rectal cancer is often contained within the rectum. But if left untreated, it can spread to other organs, most often the liver and lungs.

A small percentage of rectal cancer is due to genetic causes that may be passed from parents to children. 

Should I get screened for colorectal cancer?
Colorectal cancer can usually be cured if found early enough.

Memorial Sloan Kettering’s guidelines recommend that you get screened for colorectal cancer every ten years beginning at age 50, if you have an average risk and no symptoms. If you are at a higher risk, you should have screenings more often, depending on your age as well as your personal and family medical history.

At MSK, a colonoscopy is the preferred colorectal cancer screening method. This procedure detects polyps. These abnormal growths of tissue inside the colon and rectum can grow into cancer. A colonoscopy can also remove polyps before they become cancerous.

How is rectal cancer diagnosed?
If rectal cancer is suspected, a specialist will do a colonoscopy. This is a test in which a small piece of tissue is removed to look for signs of cancer. This sample is examined under a microscope by a pathologist (a doctor who specializes in diagnosing disease).

If you are diagnosed with rectal cancer, the next step is determining how advanced the disease is. This is called staging. Your care team may recommend CT and MRI scans and other tests to see if the cancer has spread outside the rectum to other organs.

What are the types of rectal cancer?
The vast majority of rectal cancer is a type called adenocarcinoma. This is a cancer of the cells that line the inside surface of the rectum. Rarer tumor types include:

• carcinoid tumors, which start in hormone-producing cells in the intestines
• gastrointestinal stromal tumors (a type of soft tissue sarcoma that can be found anywhere in the gastrointestinal tract but is rare in the rectum) or other types of sarcoma that start in the blood vessels or connective tissue of the rectum
• lymphoma, which is a cancer of the immune system that more commonly starts in the lymph nodes but can start in the rectum

What are the treatments for rectal cancer?

There are several ways to treat rectal cancer depending on the stage and location of the disease. These methods are often used in combination, including:

• Surgery to remove the cancer. Early-stage rectal cancer can often be treated with a minimally invasive procedure, which uses a smaller incision (cut) than traditional surgery. 
• Chemotherapy with drugs that shrink or kill cancer cells. This can be done before, during, or after surgery.
• Radiation using high-energy rays or radioactive seeds to shrink or kill cancer cells. These therapies use sophisticated, highly precise imaging tools to deliver powerful doses of radiation directly to a tumor while avoiding damage to normal cells.