Rectal cancer originates in the rectum, an approximately six-inch chamber of the colon that begins at the end of the large intestine and terminates at the anus. Rectal cancer and colon cancer (which originates in the large intestine) share many characteristics and are collectively referred to as colorectal cancer.
Rectal cancer occurs when healthy cells in the lining of the rectum undergo changes that cause them to grow uncontrollably and live beyond their normal lifespan (rectal cells usually die in about four days). The abnormal cells then build up, bind together and form precancerous growths (polyps). Over time, some types of rectal polyps can progress and become cancerous.
If cancer forms in a rectal polyp, it may grow into the walls of the rectum or colon and invade blood vessels or lymph vessels. After entering the bloodstream or lymphatic system, the cancerous cells can travel to distant areas of the body (metastasize).
What causes rectal cancer?
The precise causes of the cellular mutations that lead to rectal cancer are not yet fully understood by scientists in the general medical community. However, researchers have identified several risk factors for rectal cancer, including:
- A family history of colorectal cancer or polyps
- A personal history of inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis, or colorectal polyps
- An inherited gene mutation, such as Lynch syndrome or familial adenomatous polyposis (FAP)
- Advanced age (most rectal cancer cases are diagnosed after age 50)
What are the symptoms of rectal cancer?
Early-stage rectal cancer is often asymptomatic, although some people notice a change in their bowel habits, such as more frequent or urgent bowel movements, constipation, diarrhea, narrow stool or bloody stool. As a rectal tumor progresses, it may also cause pelvic pain, weight loss and fatigue. In many cases, precancerous or cancerous cells are detected in the rectum during a routine screening test, such as a colonoscopy, before the cancer causes symptoms.
How is rectal cancer diagnosed?
Routine screening tests can identify both precancerous and cancerous polyps in the colon and rectum. Many experts recommend that individuals at average risk for colorectal cancer begin screening around age 50.
One of the most commonly used screening tests for colorectal cancer is a colonoscopy. During this outpatient procedure, a physician inserts a long, flexible instrument (colonoscope) into the patient’s anus, then guides it into the rectum and colon. The colonoscope has a tiny camera attached to the end, which the physician uses to capture detailed images of the inner rectum and colon. The images are displayed in real time on an external monitor. If the physician identifies any polyps or other growths, he or she can use the colonoscope to remove the suspicious tissues for further analysis in a lab. The results of the lab test can help the physician confirm or rule out a diagnosis of rectal cancer.
How is rectal cancer treated?
Rectal cancer treatment can vary depending on the location, size and stage of the tumor. If the tumor is confined to the inner lining of the rectum, it may be removed through the rectum with minimally invasive surgery, and further treatment may be unnecessary.
If the tumor has invaded the rectal walls but has not progressed any further, it may be removed through the rectum with minimally invasive surgery, such as local transanal resection (if the tumor is situated in the lower rectum), or transanal endoscopic surgery (if the tumor is situated in the upper rectum). The latter procedure involves the use of a flexible tube with a light and camera attached (endoscope) to help the surgeon better visualize the tumor.
If the tumor cannot be removed through the rectum, a traditional open procedure may be considered, such as:
- Anterior resection. To remove a tumor in the upper rectum, the surgeon will remove the section of the rectum containing the tumor, then reattach the colon to the remaining part of the rectum.
- Low anterior resection. To remove a tumor in the middle or lower rectum, the surgeon will remove the entire rectum, then perform a coloanal anastomosis to attach the colon to the anus. During anastomosis surgery, the surgeon may create a small pouch in the colon to collect stool.
- Abdominoperineal resection (APR). To remove a tumor in the lower rectum, the surgeon will remove the lower (sigmoid) colon, rectum, anus and sphincter muscles. During APR surgery, the surgeon will create a stoma to bring the lower end of the colon outside the body through the skin in the lower belly. After surgery, a colostomy pouch will be worn over the stoma to collect stool.
Additional treatment with chemotherapy or radiation therapy may be administered either before or after rectal cancer surgery, depending on the stage of the tumor and other factors.
Moffitt Cancer Center
As Florida’s top cancer hospital, Moffitt Cancer Center is changing the model. In addition to taking an individualized approach to rectal cancer treatment, we emphasize prevention and offer a full spectrum of advanced screening and diagnostic tests, including colonoscopies and endoscopic ultrasounds. Our experienced pathologists thoroughly analyze each polyp and tissue sample for the presence of precancerous and cancerous cells. After evaluating the lab results, our multispecialty team of oncologists and supportive care specialists collaboratively determine the optimal treatment approach.
For patients who have been diagnosed with rectal cancer, Moffitt offers both traditional and cutting-edge treatment options, including the latest innovations in surgery, chemotherapy, radiation therapy, targeted therapy and immunotherapy. Our understanding of rectal cancer is not only extensive but also expanding on a near-daily basis. In recognition of our groundbreaking research and robust clinical trials program, we have earned a Comprehensive Cancer Center designation from the National Cancer Institute.
To learn more about rectal cancer treatment or screening options, call 1-888-663-3488 or complete our new patient registration form online to request an appointment with a specialist in our renowned Gastrointestinal Oncology Program. After you contact Moffitt Cancer Center, you will have access to wide-ranging cancer expertise as soon as possible.