Rectal cancer is a disease in which malignant (cancer) cells form in the tissues of the rectum.
The rectum is part of the body’s digestive system. The digestive system takes in nutrients (vitamins, minerals, carbohydrates, fats, proteins, and water) from foods and helps pass waste material out of the body. The digestive system is made up of the esophagus, stomach, and the small and large intestines. The colon (large bowel) is the first part of the large intestine and is about 5 feet long. Together, the rectum and anal canal make up the last part of the large intestine and are 6-8 inches long. The anal canal ends at the anus (the opening of the large intestine to the outside of the body).
Risk factors for colorectal cancer include the following:
- Having a family history of colon or rectal cancer in a first-degree relative (parent, sibling, or child)
- Having a personal history of cancer of the colon, rectum, or ovary
- Having a personal history of high-risk adenomas (colorectal polyps that are 1 centimeter or larger in size or that have cells that look abnormal under a microscope)
- Having inherited changes in certain genes that increase the risk of familial adenomatous polyposis (FAP) or Lynch syndrome (hereditary nonpolyposis colorectal cancer)
- Having a personal history of chronic ulcerative colitis or Crohn disease for 8 years or more
- Having three or more alcoholic drinks per day
- Smoking cigarettes
- Being black
- Being obese
- Older age is a main risk factor for most cancers. The chance of getting cancer increases as you get older
Signs of rectal cancer include a change in bowel habits or blood in the stool. These and other signs and symptoms may be caused by rectal cancer or by other conditions. Check with your doctor if you have any of the following:
- Blood (either bright red or very dark) in the stool
- A change in bowel habits:
- Feeling that the bowel does not empty completely
- Stools that are narrower or have a different shape than usual
- General abdominal discomfort (frequent gas pains, bloating, fullness, or cramps)
- Change in appetite
- Weight loss for no known reason
- Feeling very tired
Tests used to diagnose rectal cancer include the following:
- Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
- Digital rectal exam (DRE): An exam of the rectum. The doctor or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual. In women, the vagina may also be examined.
- Colonoscopy: A procedure to look inside the rectum and colon for polyps (small pieces of bulging tissue), abnormal areas, or cancer. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope to check for signs of cancer. Tumor tissue that is removed during the biopsy may be checked to see if the patient is likely to have the gene mutation that causes HNPCC. This may help to plan treatment. The following tests may be used:
- Reverse transcription–polymerase chain reaction (RT–PCR) test: A laboratory test in which cells in a sample of tissue are studied using chemicals to look for certain changes in the structure or function of genes.
- Immunohistochemistry: A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.
- Carcinoembryonic antigen (CEA) assay: A test that measures the level of CEA in the blood. CEA is released into the bloodstream from both cancer cells and normal cells. When found in higher than normal amounts, it can be a sign of rectal cancer or other conditions.
There are different types of treatment for patients with rectal cancer.
Five types of standard treatment are used:
- Radiation therapy
- Active surveillance
- Targeted therapy
The prognosis (chance of recovery) and treatment options depend on the following:
- The stage of the cancer (whether it affects the inner lining of the rectum only, involves the whole rectum, or has spread to lymph nodes, nearby organs, or other places in the body)
- Whether the tumor has spread into or through the bowel wall
- Where the cancer is found in the rectum
- Whether the bowel is blocked or has a hole in it
- Whether all of the tumor can be removed by surgery
- The patient’s general health
- Whether the cancer has just been diagnosed or has recurred (come back)