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Rectal Cancer

Rectal Cancer Facts

  • Rectal cancer is the growth of abnormal cancerous cells in the lower part of the colon that connects the anus to the large bowel.
  • Rectal cancer develops usually over years; its actual cause is not known, but risk factors include increasing age (over 50), smoking, family history, high-fat diet, or a history of polyps or colorectal cancer or inflammatory bowel disease.
  • The major symptom of rectal cancer is bleeding from the rectum; other symptoms include anemia, fatigue, shortness of breath, dizziness and/or a fast heartbeat, bowel obstruction, small diameter stools, and weight loss.
  • For diagnosis, exams and tests may include fecal occult blood testing, endoscopy, digital rectal examination, sigmoidoscopy, CT/MRI imaging studies, along with routine blood tests and detection of carcinoembryonic antigen (CEA).
  • Medical treatment depends on the stage of rectal cancer (stages I-IV), with IV being the most severe stage; multiple chemotherapy medications are available and are chosen by the specialist (oncologist) to fit the individual's stage of rectal cancer.
  • Surgery is used to both treat and reduce symptoms and, in some individuals, may result in a remission of the cancer.
  • Radiation therapy is also used to kill or shrink rectal cancers.
  • Follow-up is important to make sure that rectal cancer does not recur.
  • Prevention involves detection and removal of precancerous growths.
  • The outlook or prognosis for individuals with rectal cancer is usually related to the stage of cancer, with stages III and IV having the poorest outcomes.

Rectal Cancer Overview

The rectum is the lower part of the colon that connects the large bowel to the anus. The rectum's primary function is to store formed stool in preparation for evacuation. Like the colon, the three layers of the rectal wall are as follows:

  • Mucosa: This layer of the rectal wall lines the inner surface. The mucosa is composed of glands that secrete mucus to help the passage of stool.
  • Muscularis propria: This middle layer of the rectal wall is composed of muscles that help the rectum keep its shape and contract in a coordinated fashion to expel stool.
  • Mesorectum: This fatty tissue surrounds the rectum.

In addition to these three layers, another important component of the rectum is the surrounding lymph nodes (also called regional lymph nodes). Lymph nodes are part of the immune system and assist in conducting surveillance for harmful materials (including viruses and bacteria) that may be threatening the body. Lymph nodes surround every organ in the body, including the rectum.

The American Cancer Society (ACS) estimates about 93,000 new cases of colon cancer and 39,600 new cases of rectal cancer will occur in 2015. Males are more likely than females to develop rectal cancer (about 23,000 males to 16,000 females in 2015). The most common type of rectal cancer is adenocarcinoma (95%), which is a cancer arising from the mucosa. Cancer cells can also spread from the rectum to the lymph nodes on their way to other parts of the body.

Like colon cancer, the prognosis and treatment of rectal cancer depends on how deeply the cancer has invaded the rectal wall and surrounding lymph nodes (its stage, or extent of spread). However, although the rectum is part of the colon, the location of the rectum in the pelvis poses additional challenges in treatment when compared with colon cancer.

This article only discusses issues related to rectal adenocarcinoma.

Medically Reviewed by a Doctor on 7/22/2015

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