Rectal cancer is cancer that develops in cells in the rectum. The rectum is located below the sigmoid colon and above the anus.

Your rectum and colon are both part of the digestive system, so rectal and colon cancers are often grouped under the term colorectal cancer.

Worldwide, colorectal cancer is the second most common cancer in females and the third most common cancer in males.

The American Cancer Society estimates there will be 43,340 new cases of rectal cancer in the United States in 2020. This compares with 104,610 new cases of colon cancer.

Some symptoms of rectal cancer could be due to other conditions. These symptoms include:

  • weakness and fatigue
  • appetite changes
  • weight loss
  • frequent abdominal discomfort, gas, cramps, pain

Other signs and symptoms of rectal cancer include:

Use this interactive 3-D diagram to explore colorectal cancer.

No matter where it starts, cancer can spread, or metastasize, through tissue, the lymph system, or the bloodstream to reach other parts of the body.

Staging cancer indicates how far the cancer has progressed, which can help your doctor decide the best treatment.

Below are the stages of rectal cancer.

Stage 0 (carcinoma in situ)

Only the innermost layer of the rectum wall contains abnormal cells.

Stage 1

Cancer cells have spread past the innermost layer of the rectum wall, but not to lymph nodes.

Stage 2

Cancer cells have spread into or through the outer muscle layer of the rectum wall, but not to lymph nodes. This is often referred to as stage 2A. In stage 2B, the cancer has spread into the abdominal lining.

Stage 3

Cancer cells have spread through the outermost muscle layer of the rectum and to one or more lymph nodes. Stage 3 is often broken up into substages 3A, 3B, and 3C based on the amount of lymph tissue affected.

Stage 4

Cancer cells have spread to distant sites, like the liver or lungs.

Mistakes in DNA can cause cells to grow out of control. Faulty cells pile up to form tumors. These cells can penetrate and destroy healthy tissue. What sets off this process isn’t always clear.

There are some inherited gene mutations that can increase risk. One of these is hereditary nonpolyposis colorectal cancer, known as Lynch syndrome. This disorder raises the risk of colon and other cancers, especially before age 50.

Another such syndrome is familial adenomatous polyposis. This is a rare disorder that can cause polyps in the lining of the colon and rectum. Without treatment, it can raise the risk of colon or rectal cancer, especially before age 40.

Other risk factors for rectal cancer are:

  • Age. Diagnosis usually occurs after age 50, although rates are increasing among younger people.
  • Race. Black Americans are at higher risk than other groups of developing rectal cancer. One reason for this may be inequities in healthcare access.
  • Family history. Personal or family history of colorectal cancer can raise risk.
  • Radiation therapy. Previous radiation treatment to the abdomen can increase risk.

Other conditions that may increase risk include:

Some lifestyle factors that may play a role in colorectal cancer are:

  • diet with too few vegetables and too much red meat, particularly well-done meat
  • lack of exercise
  • smoking
  • consuming more than three alcoholic drinks a week

Your doctor will likely begin by taking your medical history and performing a physical examination. This may include inserting a gloved finger into your rectum to feel for lumps.

Your doctor might next recommend a fecal immunochemical test (FIT) or a sigmoidoscopy. The screening schedule for these tests will vary depending on your risk level. If these tests are positive for cancer, a colonoscopy is the next step.

In a colonoscopy, your doctor uses a thin tube with a light and camera at the end to view the inside of your rectum and colon. They can usually remove any polyps they find at this time.

During the colonoscopy, your doctor can also collect tissue samples for later examination in a lab. These samples can be viewed under a microscope to determine if they’re cancerous. They can also be tested for genetic mutations associated with colorectal cancer.

Your doctor may also order a blood test. A high level of carcinoembryonic antigen, a substance made by cancerous tumors, in your bloodstream may indicate rectal cancer.

Once your doctor makes their diagnosis of rectal cancer, their next step is to determine how far it might have spread.

Your doctor can use an endorectal ultrasound to examine your rectum and surrounding area. For this test, your doctor inserts a probe into your rectum to produce a sonogram, a type of image.

Your doctor may use other imaging tests to look for signs of cancer throughout your body. These include:

  • X-ray
  • CT or PET scan
  • MRI

In recommending treatment, your doctor will consider:

  • tumor size
  • where cancer may have spread
  • your age
  • your general health

This helps them determine the best combination of treatments, as well as the timing of each treatment.

Below are the general guidelines for treatment by stage.

Stage 0

  • removal of suspicious tissue during colonoscopy
  • removal of tissue during a separate surgery
  • removal of tissue and part of the surrounding area

Stage 1

  • local excision or resection
  • radiation therapy
  • chemotherapy

Stages 2 and 3

  • surgery
  • radiation therapy
  • chemotherapy

Stage 4

  • surgery, possibly in more than one area of the body
  • radiation therapy
  • chemotherapy
  • targeted therapies, such as monoclonal antibodies or angiogenesis inhibitors
  • cryosurgery, a procedure that uses a cold liquid or a cryoprobe to destroy abnormal tissue
  • radiofrequency ablation, a procedure in which radio waves are used to destroy abnormal cells
  • a stent to keep the rectum open if it’s blocked by a tumor
  • palliative therapy to improve overall quality of life

You can also ask your doctor about clinical trials that might be a good fit for you.

Advances in treatment over the last few decades have improved the overall outlook. In fact, many cases of rectal cancer can be cured. The overall 5-year survival rate is 67 percent.

The 5-year relative survival rate by stage is:

  • Localized: 89 percent
  • Regional: 71 percent
  • Distant: 15 percent

It’s important to note that these figures are based on information between 2009 and 2015. Since then, treatments have been modified and improved. These numbers may not reflect current survival rates.

Here are a few other details that must be factored in:

  • where cancer may have spread
  • whether your bowel is blocked
  • if the entire tumor can be surgically removed
  • age and general health
  • whether this is a recurrence
  • how well you tolerate treatment

When it comes to your individual outlook, the best source of information is your own doctor.