Rectal Cancer

Rectal cancer occurs when the cells in the lining of the rectum change and form malignant (cancerous) tumors. Rectal cancer is often grouped with colon cancer, known as colorectal cancer, and is the fourth most common cancer in the United States.

About Rectal Cancer

The rectum and the colon make up the large intestine, or large bowel. The rectum makes up the last six inches of the large intestine and connects the colon to the anus. Colon cancer and rectal cancer are often grouped together (colorectal cancer), because they share many of the same characteristics and are often treated similarly. Most rectal cancers start as a growth, called a polyp, on the inner lining of the colon or rectum. While not all polyps progress to cancer, some can change into cancer over time, usually over the course of many years. Polyps may be small and produce few, if any, symptoms. For this reason, doctors recommend regular screening tests to help prevent colon cancer by identifying and removing polyps before they turn into cancer.

There are various factors that can increase the risk of a polyp developing into cancer such as a polyp larger than one centimeter, more than three polyps found, and if dysplasia, or the presence of abnormal cells, is seen in a polyp after removal.

Types of polyps include:

• Adenomatous polyps (adenomas) sometimes change into cancer. Because of this, adenomas are called a pre-cancerous condition. The 3 types of adenomas are tubular, villous, and tubulovillous.
• Hyperplastic polyps and inflammatory polyps are more common, but in general they are not pre-cancerous. Some people with large (more than 1 cm) hyperplastic polyps might need colorectal cancer screening with colonoscopy more often to monitor the polyp.
• Sessile serrated polyps (SSP) and traditional serrated adenomas (TSA) are often treated like adenomas because they have a higher risk of colorectal cancer

Types of Rectal Cancer

Most rectal cancers are adenocarcinomas, which means the cancer starts in the cells that make the mucus that lubricates the inside of the colon and rectum.

Other, less common types of tumors can also develop in the colon and rectum and include:

• Carcinoid tumors develop from special hormone-making cells in the intestine.
• Gastrointestinal stromal tumors (GISTs) develop from special cells in the wall of the colon called the interstitial cells of Cajal. Some are benign (noncancerous). These tumors can be found anywhere in the digestive tract but are not common in the colon.
• Lymphomas are cancers of immune system cells. They mostly develop in lymph nodes, but they can also develop in the colon, rectum, or other organs. Information on lymphomas of the digestive system can be found in non-Hodgkin lymphoma.
• Sarcomas can develop in blood vessels, muscle layers, or other connective tissues in the wall of the colon and rectum. Sarcomas of the colon or rectum are rare.
• Melanoma is a cancer that develops from cells called melanocytes, which give skin its color. While melanoma usually starts in the skin, there are also small numbers of melanocytes in the mucosa, which is a tissue that lines various parts of the body, including the anus and rectum. Melanoma of the colon or rectum develops in the mucosa and is extremely rare.

Symptoms of Rectal Cancer:

• Abdominal pain
• A change in bowel habits, such as diarrhea, constipation, or more-frequent bowel movements
• A feeling that your bowel doesn’t empty completely
• Change in appetite
• Dark maroon or bright red blood in stool
• Narrow stool
• Unintended weight loss
• Weakness or fatigue

Risk Factors for Rectal Cancer

Certain people are at greater risk of developing rectal cancer.

Risk factors for rectal cancer may include:

• Age: Rectal cancer can occur at any age, but usually affects those above age 50.
• Family history: A family history of colon or rectal cancer can increase your risk of rectal cancer, as can inherited changes in certain genes that increase the risk of familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary nonpolyposis colorectal cancer). Additionally, African Americans are at higher risk of developing rectal cancer than patients of other racial backgrounds.
• Health history: Rectal cancer is associated with a history of the following
  • Cancer of the colon, rectum, or ovary,
  • High-risk adenomas, or colorectal polyps that are one centimeter or larger in size or that have cells that look abnormal
  • Inflammatory bowel disease
  • Chronic ulcerative colitis or Crohn’s disease
• Personal history: Excessive alcohol consumption, smoking, lack of physical activity, and obesity are all linked to rectal cancer risk.

Treating Rectal Cancer at UT Medicine

Treatment requires accurate diagnosis and a care plan tailored to the specific type of tumor, the tumor’s location, and the overall needs of the patient. The different behavior of different tumor types helps drive decisions about treatment, which may include combinations of surgery, radiation therapy, and chemotherapy.