References:Rectal Cancer(Chinese Version)

Rectal Cancer: The Basics

Carolyn Coyle, MSN, RN, AOCN OncoLink Posting Date: February 28, 2003 What is the rectum?

The rectum is located at the end of the colon and is about 5 inches in length. The rectum is normally empty, except just prior to having a bowel movement. Stool is propelled, by the colon, into the rectum and is then excreted through the anal canal. The anal canal has two muscular "valves", called the internal and external sphincters, through which the stool must pass. The sphincters allow us to retain stool until we are ready to have a bowel movement, at which time the sphincters relax, releasing the stool.

What is rectal cancer?

Rectal cancer is malignant (or cancerous) tissue that grows in the wall of the rectum. The majority of tumors begin when normal tissue in the rectum wall forms an adenomatous polyp, or pre-cancerous growth, projecting from the rectal wall lining. As this polyp grows larger, the tumor is formed. This process can take many years, which allows time for early detection with screening tests.

Am I at risk for rectal cancer?

In 2003, there will be an estimated 42,000 new cases of colon cancer in the United States (23,800 in men and 18,200 in women). In general, colon and rectal cancers are grouped together and have the same risk factors associated with them. The average age of diagnosis is 66 years of age, and risk increases with age. Individuals with a personal or family history of colorectal cancer or polyps, inherited colorectal cancer syndromes (i.e., FAP and HNPCC, and patients with ulcerative colitis or Crohn's disease are at higher risk, and may require screening at an earlier age than the general population. A person with one first degree relative (parent, sibling or child) with colon cancer is 2 to 3 times as likely to develop the cancer as someone who does not have an affected relative.

However, this does not mean that people without a family history are not at risk. About 80% of new colorectal cancer cases are diagnosed in people who would not be identified as being at high risk. Studies of colorectal cancer cases found that lifestyle factors may put a person at higher risk. These factors include: a diet high in fat and red meat, low in fruits and vegetables, high caloric intake, low levels of physical activity, and obesity. In addition, smoking and excessive alcohol intake may play a role in colorectal cancer development. Despite avoiding all of these factors, some people will still develop colon or rectal cancer. With screening and early detection, these patients can be cured in a majority of the cases.

How can I prevent rectal cancer?

Given the things that put a person at higher risk, a low-fat diet high in fruits and vegetables and low in red meat, getting regular exercise, and maintaining a healthy body weight may aide in prevention. The term chemoprevention can be defined as 'the use of a chemical compound to prevent, inhibit, or reverse the formation of the cancer'. There are studies ongoing looking at vitamins A, E, D, and C, folic acid, calcium, selenium, aspirin, cox-2 inhibitors, and hormone replacement therapy as chemopreventive agents, that may prevent or reverse the formation of polyps and colorectal cancer. These studies, thus far, have been inconclusive, so no specific recommendations have been made for the general population. Some of these agents continue to be evaluated in clinical trials.

What screening tests are available?

The one screening test that is specific to rectal cancer is a digital rectal exam (DRE). This test consists of a physician inserting a gloved finger into the patient?s rectum and feeling for abnormal growths or strictures. Studies have not proven that screening with DRE actually decreases deaths due to rectal cancer. Other screening tests are the same as those used for colon cancer screening, including fecal occult blood testing, colonoscopy, and sigmoidoscope. These tests screen both the colon and the rectum.

Some tumors and polyps may bleed intermittently, and this blood can be detected in stool samples by a test called fecal occult blood testing (FOBT). By itself, FOBT only finds about 24% of cancers. It is recommended by the American Cancer Society that FOBT be done annually, in conjunction with a flexible sigmoidoscopy, every 5 years after age 50. This combination of tests detects about 76% of colorectal tumors. The sigmoidoscope is a slender, flexible tube that has the ability to view the rectum and about ? of the colon. If a polyp or tumor is detected with this test, the patient must be referred for a full colonoscopy.

The colonoscope is similar to the sigmoidoscope, but is longer, and can view the entire rectum and colon. If a polyp is found, the physician can remove it, and send it to a pathology lab to determine if it is adenomatous (cancerous). As a screening method, the American Cancer Society recommends that a colonoscopy be done every 10 years, after age 50. Patients with a family or personal history should have more frequent screenings; beginning at an age ten years younger than their relative was at diagnosis. Patients with a history of ulcerative colitis are also at increased risk and should have more frequent screening than the general public. Patients should talk with their physician about which screening method is best for them, and how often it should be performed. You can learn more about screening by reading Basic Information about Colorectal Cancer and Colorectal Cancer Screening. You can learn about two new tests still in development, virtual colonoscopy and DNA stool testing.

What are the signs of rectal cancer?

Unlike colon cancers, most rectal cancers cause symptoms. These include: red blood seen in the stool, unexplained constipation, alternating with diarrhea, changes in the diameter of stool (patients may notice "pencil-thin stools"), and tenesmus, which is a sensation of having to have a bowel movement when you don?t, and a feeling of being unable to empty the rectum. If tumors have become more advanced, they can invade the nerves leading to the bladder and cause incontinence or pain due to pressure in the buttocks or perineum.

How is rectal cancer diagnosed and staged?

Once rectal cancer is found by the screening tests, further tests are needed to determine the extent of the tumor. The tests used to determine spread of the tumor are CT scans, MRIs, and endoscopic ultrasound (EUS). The EUS is an ultrasound, which uses sound waves to determine the depth of the tumor and if surrounding lymph nodes are involved. With these tests, a stage is determined, which dictates the necessary treatment. The stages are:

Stage 0: the tumor is confined to the first layer of the rectal tissue. It is also called carcinoma in situ

Stage I: the tumor has spread through the innermost lining of the rectum into the second and third layers of the inside wall of the rectum, but has not spread outside the rectum

Stage II: the tumor has spread through the rectal wall into surrounding tissue, but has not spread to the lymph nodes

Stage III: the tumor has spread to the surrounding lymph nodes, but has not spread to other areas of the body

Stage IV: the tumor has spread to other areas of the body, such as the liver and lungs

What are the treatments for rectal cancer?

Surgery

Over the past twenty years there have been significant improvements in surgical techniques for the treatment of rectal cancer. In the past, a majority of patients required a colostomy after surgery to remove a rectal tumor and developed significant side effects (incontinence and male impotence) due to nerve damage that frequently occurred during the surgery. The utilization of pre-operative chemoradiation and improved surgical techniques have led to fewer side effects and fewer patients requiring colostomy.

If the tumor is relatively small, it can be removed by a procedure called local excision. A larger tumor requires a resection (removal of the tumor and the tissue surrounding it) and anastomosis (the two tumor-free ends of the bowel are reconnected). If the bowel ends cannot be reconnected, a colostomy is made.

The normal rectum acts as a holding area for stool. When a rectal resection and anastomosis is performed, that holding area is lost, leading to more frequent bowel movements and incontinence. To alleviate this problem, the colonic J pouch was developed. This procedure uses the remaining bowel to create a J-shaped pouch, which acts as a new holding area for the stool, about 5-6 cm in length, significantly reducing the number of bowel movements and incontinence.

Radiation and Chemotherapy

Patients with stage 0 and I disease are treated with surgery only. Patients with stage II and III disease are at a high risk of recurrence and should be treated with chemoradiation either pre or post operatively. Studies have shown that giving fluorouracil (5-FU) in combination with radiation therapy (called chemoradiation) is more effective than radiation alone. Because of the size of the pelvis (bony structure that the rectum lies in), it is often difficult, with larger tumors, for a surgeon to remove enough tissue to have adequate tumor-free margins. Giving chemoradiation pre-operatively can shrink a tumor that would not have been surgically removable, therefore making them candidates for potentially curative surgery. This is known as downstaging the tumor. Downstaging has also allowed patients with tumors that would require a colostomy, to have a resection and anastomosis following treatment with chemoradiation.

Patients with stage IV rectal cancer may be offered resection of the tumor, radiation and/or chemotherapy. Some patients may be candidates for surgical removal of the parts of organs where the cancer may have spread (i.e. liver, ovaries). Most of these treatments are to alleviate symptoms, but are not considered curable.

Follow-up care

Once a patient has completed chemotherapy, they must be followed closely for recurrence. The guidelines for follow-up surveillance, written by the National Comprehensive Cancer Network are: physical exam (including digital rectal exam) every 3 months for 2 years, then every 6 months for 3 years, CEA level checked every 3 months for 2 years, then every 6 months for 3 years, and colonoscopy in 1 year, repeat in 1 year if abnormal, or every 3 years if no polyps are found. There is not enough evidence to support or refute the use of chest x-ray or CT scan for surveillance at this time, so this varies from physician to physician.

Clinical trials have, and continue to play an important role in the treatment of colorectal cancer. In the past 20 years, considerable improvements have been made in colorectal cancer therapy, with overall survival rates increasing from 45 to 75 percent. The treatments we have today were refined through clinical trials, and many new avenues continue to be explored. Talk with your physician about current clinical trials for colon cancer in your area.

This article is meant to give you a better understanding of rectal cancer. Use this knowledge when meeting with your physician, making treatment decisions, and continuing your search for information. You can learn more about colorectal cancer on OncoLink through the related links on the left.