Rectal cancer arises from the lining of the rectum. The rectum is the bottom 6 inches of your colon (large intestine). Like colon cancer, rectal cancer is highly curable, if detected in early stages. In comparison, colorectal cancer is referring to any cancer that may occur in the colon or rectum.
In 2017, it is estimated that nearly 40,000 new cases of rectal cancer will be diagnosed in the United States compared to more than 95,000 new cases of colon cancer.
- About one in 22 (4.5%) Americans will develop colorectal cancer during their lifetime.
- Colorectal polyps (benign, abnormal growths) affect about 20%-30% of American adults.
- Age: More than 90% of people are diagnosed with colon cancer after age 50
- Family history of colorectal cancer (especially parents or siblings).
- Personal history of Crohn’s Disease or ulcerative colitis for 8 years or longer
- Colorectal polyps
- Personal history of breast, uterine or ovarian cancer
Rectal cancer is preventable. Nearly all cases of rectal cancer develop from polyps. These polyps are benign growths on the inner lining of the rectum. Detection and removal of polyps through colonoscopy reduces the risk of rectal cancer. Rectal cancer screening recommendations are based on medical and family history. Screening typically starts at age 50 in patients with average risk. Those at higher risk are usually advised to receive their first screening at a younger age.
While it is not definitive, there is some evidence that diet may play a significant role in preventing colorectal cancer. A diet high in fiber (whole grains, fruits, vegetables and nuts) and low in fat may help prevent colorectal cancer.
Rectal cancer often causes no symptoms and is detected during routine screenings. It is important to note that other common health problems can cause some of the same symptoms. For example, hemorrhoids are a common cause of rectal bleeding but do not cause rectal cancer.
- A change in bowel habits (e.g., constipation or diarrhea)
- Narrow shaped stools
- Bright red or very dark blood in the stool
- Ongoing pelvic or lower abdominal pain (e.g., gas, bloating or pain)
- Unexplained weight loss
- Nausea or vomiting
- Feeling tired all the time
Abdominal pain and weight loss are typically late symptoms, indicating possible extensive disease. Anyone who experiences any of the above symptoms should see a physician as soon as possible.
- Medical history
- Physical exam
- Blood tests
- Digital rectal exam (DRE): Insertion of a gloved, lubricated finger into the rectum to check for abnormalities
- Proctoscopy: Examination of the anal cavity and rectum using a narrow instrument called a proctoscope
- Colonoscopy: Examination of the entire colon with a long, flexible instrument called a colonoscope
- Biopsy: Taking samples of tissues so they can be viewed under a microscope to check for signs of cancer
Rectal Cancer Staging Tests
- Computed Tomography (CT) scan: A highly sensitive x-ray test that allows physicians to see “inside” the body and look at all of the organs. This test can help detect the presence of cancer that has spread outside the rectum.
- Positron emission tomography (PET) scan: An imaging test that uses a special dye that has radioactive tracers. This allows physicians to identify areas where cancer may have spread outside the rectum.
- CEA assay: Carcinoembryonic antigen is a substance in the blood that may be elevated when cancer is present. Although not completely conclusive on its own, this test is used to help monitor patients after their cancer has been treated.
- An imaging test that uses a magnetic field and pulses of radio wave energy to create pictures of organs and structures inside the body. This helps determine if the tumor has spread through the wall of the rectum and invaded nearby structures.
- Endoscopic ultrasound (EUS): A procedure in which an endoscope is inserted into the rectum. An ultrasound can then be performed to determine how far into the rectal wall the cancer has grown.
Surgery to remove rectal cancer is almost always required for a complete cure. Depending on the location and stage, this may be performed through the anus (opening of the rectum) or through the abdomen. The tumor and lymph nodes are removed, along with a portion of normal rectum on either side of the tumor. A colostomy is a surgically created opening that connects a part of the colon to the skin of the abdominal wall. This procedure is typically only done in a very small number of rectal cancer patients.
Minimally invasive surgical techniques may be used by trained surgeons based on the individual case. Your surgeon will discuss this with you prior to surgery and decide on the best approach.
Chemotherapy or radiation therapy may be offered either before or after surgery, depending on the stage of the cancer.
Prognostic (Outcome) Factors
Early detection through screening methods like colonoscopy is crucial. Patient outcome is strongly associated with the rectal cancer stage at the time of diagnosis. Prognostic factors include:
- Cancer stage (how advanced the cancer is)
- Cancer location in the rectum
- Whether the bowel is blocked or has a hole in it
- Whether all of the tumor can be removed surgically
- Patient’s general health and ability to tolerate different treatments
- Whether the cancer is newly diagnosed or has recurred (come back)
Follow-up care after treatment for rectal cancer is important. Even when the cancer appears to have been completely removed or destroyed, the disease may recur. Undetected cancer cells can remain in the body after treatment. Your colon and rectal surgeon will monitor your recovery and check for cancer recurrence at specific intervals. Blood tests, clinical examinations, and imaging tests may be performed based on the stage of cancer.