Rectal Cancer: Patient Education

Cancer Facts

According to the American Society of Clinical Oncology:

  • Colorectal cancer is the third most common cancer among both men and women in the United States.
  • Colorectal cancer is the third most common cause of cancer death among men and women separately (and the second most common cause of cancer death in men and women combined) in the United States.

“Colorectal cancer is a disease that affects both men and women, all races, and can be prevented by the removal of small, precancerous polyps from the colon,” says Andrejs Avots-Avotins, MD, Gastroenterology, and Chairman of the Scott & White Board of Directors.

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Rectal cancer is a group of malignant cells that starts in the tissues of your rectum. The growing tumor can affect the function of your rectum as well as spread (metastasize) to other parts of your body.

Your rectum is part of your digestive system, also called your gastrointestinal (GI) tract. The organs in your digestive system break down and absorb the food you eat and convert it into products your body can use to stay healthy. Your GI tract, in particular your colon and rectum, eliminates the products your body cannot use.

Food enters your body through your mouth. You chew it and swallow it through your throat (esophagus), where it travels into your stomach. There it’s partly broken down by your stomach acids. It then moves into your small intestine (also called the small bowel).  Your small intestine is narrow; it’s about 20 feet long. There, your food is further broken down and nutrients absorbed into your body.

In the lower right-hand side of your abdomen, your small intestine joins your large intestine (also called the large bowel). Your large intestine is largely made up of colon, or a muscular tube about 5 feet long. Water and salt remaining in your food are absorbed by your large intestine; your large intestine also serves as a holding place for your waste matter (feces, or stool). The last 6 inches is your rectum, which ends at your anus. Waste exits your body through your anus.

How Rectal Cancer Begins

Rectal cancer generally begins as a noncancerous (benign) polyp growing on the inner lining of your rectum. A polyp is a tumor. Some polyps remain benign, while others become cancerous (malignant).

Polyps can remain benign for a long time. It can often take years for cancer to develop, and even then, rectal cancer can be slow growing. However, because precancerous polyps are potentially life threatening, your GI Cancer Team recommends removing them to prevent rectal cancer.

Cancerous polyps can grow into the lining of your rectum. From there, the cancer can spread into your blood vessels or your lymphatic vessels. Lymphatic vessels are small tubes or veins that carry lymph, a clear fluid that contains immune system cells and that carries excess waste products from your tissues.

If cancer cells enter your lymph system, they can easily spread throughout your body, starting new tumors.

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