Rectal cancer is cancer that develops in cells in the rectum.

Your rectum and colon are both part of the digestive system, so rectal and colon cancers are often grouped under the term colorectal cancer. The rectum is located below the sigmoid colon and above the anus.

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 43,030 new cases of rectal cancer in the United States in 2018. This compares with 97,220 new cases of colon cancer.

Some symptoms of rectal cancer could be due to other conditions. For example:

  • 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 decide treatment.

The stages of rectal cancer are:

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 rare disorder 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
  • race: African-Americans are at higher risk than people of European descent
  • personal or family history of colorectal cancer
  • previous radiation treatment to the abdomen

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 the rectum to feel for lumps.

You might also need a colonoscopy. In this procedure, a thin tube with a light and camera is used to view the inside of the rectum and colon. Any polyps found during this test can usually be removed at this time.

During the colonoscopy, tissue samples can be taken for later examination. 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 in your bloodstream may indicate rectal cancer.

Once the diagnosis of rectal cancer has been made, the next step is to determine how far it might have spread. An endorectal ultrasound can be used to examine the rectum and surrounding area. For this test, a probe is inserted into the rectum to produce a sonogram.

Other imaging tests may be used 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 determine the best combination of treatments, as well as the timing of each treatment.

General guidelines for treatment by stage are:

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 a 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 people can be cured. The overall five-year survival rate is 66.5 percent.

The five-year relative survival rate by stage is:

  • stage 1: 88 percent
  • stage 2A: 81 percent
  • stage 2B: 50 percent
  • stage 3A: 83 percent
  • stage 3B: 72 percent
  • stage 3C: 58 percent
  • stage 4: 13 percent

It’s important to note that these figures are based on information between 2004 and 2010. Since then, the staging system has been modified and treatments have evolved. 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.