Lymphedema and Colon Cancer

What is the colon?

The colon is part of a section of the digestive tract called the large intestine. The large intestine is a tube that is 5 to 6 feet in length. The first 5 feet make up the colon, which connects to about 6 inches of rectum, and ends with the anus. By the time food reaches the colon (about 3 to 8 hours after eating), the nutrients have been absorbed and it has become a liquid waste product. The colon's function is to change this liquid waste into stool. The stool can spend anywhere from 10 hours to several days in the colon. It has been suggested that the longer stool remains in the colon, the higher the risk for colon cancer, but this has not been proven.

What is colon cancer?

Colon cancer is malignant tissue that grows in the wall of the colon. The majority of tumors begin when normal tissue in the colon wall forms an adenomatous polyp, or pre-cancerous growth projecting from the colon wall. 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 Colon Cancer?

Colon cancer is the third most common type of cancer, in both males and females, in the western world. The incidence is highest in African Americans, who are also more likely to die of the disease. Certain factors put people at higher risk, but with over 135,000 new cases each year in the United States, we must all be aware of this deadly disease. The risk of colon cancer rises substantially at age 50, but every year there are numerous cases in younger people. Individuals with a personal or family history of colon cancer or polyps, inherited colon 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 colon cancer cases are diagnosed in people who would not be identified as being at high risk. Studies of colon 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 colon cancer development. Despite avoiding all of these factors, some people will still develop colon cancer. With screening and early detection, these patients can be cured in a majority of the cases.

How Can I Prevent Colon 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 colon 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?

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 colon tumors. The sigmoidoscope is a slender, flexible tube that has the ability to view about ﾽ 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 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 earlier age than their relative was diagnosed. 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.

Despite the effectiveness of screening tests for colon cancer, one study found that only 44% of adults, age 50 and older, had undergone testing. Recent media focus, including Katie Couric's efforts, has helped to raise public awareness of this cancer, but more education is needed.

What are the Signs of Colon Cancer?

Unfortunately, the early stages of colon cancer may not have any symptoms. This is why it is important to have screening tests done even though you feel well. As the polyp grows into a tumor, it may bleed or obstruct the colon, causing symptoms. These symptoms include:

Bleeding from the rectum
Blood in the stool or toilet after a bowel movement
A change in the shape of the stool (i.e. thinning)
Cramping pain in the abdomen
Feeling the need to have a bowel movement when you don't have to have one

As you can see, these symptoms can also be caused by other conditions. If you experience these symptoms, you should be checked by a doctor.

How is Colon Cancer Diagnosed and Staged?

After a cancer has been found, the stage must be determined to decide on appropriate treatment. The stage tells how far the tumor has invaded the colon wall, and if it has spread to other parts of the body.

Stage 0 (also called carcinoma in situ) - the cancer is confined to the outermost portion of the colon wall.
Stage I - the cancer has spread to the second and third layer of the colon wall, but not to the outer colon wall or beyond. This is also called Dukes' A colon cancer.
Stage II - the cancer has spread through the colon wall, but has not invaded any lymph nodes (these are small structures that help in fighting infection and disease). This is also called Dukes' B colon cancer.
Stage III - the cancer has spread through the colon wall and into lymph nodes, but has not spread to other areas of the body. This is also called Dukes' C colon cancer.
Stage IV - the cancer has spread to other areas of the body (i.e. liver and lungs). This is also called Dukes' D colon cancer.

After the tumor and lymph nodes are removed by a surgeon, they are examined by a pathologist, who determines how much of the colon wall and lymph nodes have been invaded by tumor. Patients with invasive cancer (stages II, III, and IV) require a staging workup, including full colonoscopy, carcinoembryonic antigen (CEA) level (a marker for colon cancer found in the blood), chest x-ray, and CT scan of the abdomen and pelvis, to determine if the cancer has spread.

What are the Treatments for Colon Cancer?

Surgery

Surgery is the most common treatment for colon cancer. If the cancer is limited to a polyp, the patient can undergo a polypectomy (removal of the polyp), or a local excision, where a small amount of surrounding tissue is also removed. If the tumor invades the bowel wall or surrounding tissues, the patient will require a partial resection (removal of the cancer and a portion of the bowel) and removal of local lymph nodes to determine if the cancer has spread into them. After the tumor is removed, the two ends of the remaining colon are reconnected, allowing normal bowel function. In some situations, it may not be possible to reconnect the colon, and a colostomy (an opening in the abdominal wall to allow passage of stool) is needed.

Chemotherapy

Despite the fact that a majority of patients have the entire tumor removed by surgery, as many as 40% will develop a recurrence. Chemotherapy is given to reduce this chance of recurrence. There is some controversy over patients with stage II disease receiving chemotherapy. Studies have not consistently shown a benefit in treating these patients. Generally, patients with stage II disease who present with a bowel perforation or obstruction, or have poorly differentiated tumors (determined by a pathologist), are considered at higher risk for recurrence, and are treated with 6 to 8 months of Fluorouracil (5-FU) and Leucovorin (LV) (both chemotherapy agents). Other patients with stage II disease are followed closely, but generally receive no chemotherapy. Patients who present with stage III colon cancer are typically treated with a regimen of Fluorouracil and Leucovorin for 12 months.

Forty to fifty percent of patients have metastatic (disease that has spread to other organs) at the time of diagnosis, or have a recurrence of the disease after therapy. Unfortunately, the prognosis for these patients is poor. The standard therapy for patients with advanced disease is Fluorouracil, Leucovorin, and irinotecan (CPT-11). This regimen was found to be more effective than Fluorouracil and Leucovorin alone in these patients. With this therapy, an average of 39% of patients have a response, but the average survival is still only 15 months. Patients and their physicians must weigh the benefits of therapy versus the side effects of the treatment. Younger patients and those in better physical shape are better able to tolerate therapy.

Two new medications, capecitabine (Xeloda) and oxaliplatin, are also being used in the treatment of advanced colon cancer. Capecitabine is currently approved by the FDA for the treatment of advanced colon cancer that has failed treatment, but is still being investigated in untreated patients. Oxaliplatin is widely used in Europe, but has not yet been approved by the FDA for use in the United States. Currently, patients can only receive this medication in a clinical trial.

Radiotherapy

Colon cancer is not typically treated with radiation therapy. If the cancer has invaded another organ, or adhered to the abdominal wall, radiation therapy may be one option. One way to understand this is that radiation needs a "target". If the tumor has been surgically resected, there is no target to radiate. If the tumor has spread to other organs, chemotherapy is needed to reach all the tumor cells, whereas radiation can only treat a small area.

Follow-Up Testing

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 colon cancer. In the past 20 years, considerable improvements have been made in colon 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 colon cancer. Use this knowledge when meeting with your physician, making treatment decisions, and continuing your search for information. You can learn more about colon cancer on OncoLink through the related links on the left.

References

The American Cancer Society. Facts and Figures 2002. www.cancer.org
Blumberg, D. & Ramanathan, R. K. (2002) Treatment of Colon and Rectal Cancer. Journal of Clinical Gastroenterology, 34(1), 15-26.
Lieberman, D. A. & Weiss, D. G. (2001) One-Time Screening for Colorectal Cancer with Combined Fecal Occult Blood Testing and Examination of the Distal Colon. The New England Journal of Medicine, 345(8), 555-560.
National Cancer Institute. Patient Statement on Colon Cancer.
National Comprehensive Cancer Network Practice Guidelines for Colorectal Cancer (2000). Oncology, 14(11A), 203-212.
Yarbro, C. H., Frogge, M. H., Goodman, M., & Groenwald, S. L. (Eds.): Cancer Nursing: Principles and Practice (2001). Jones and Bartlett Publishers, Boston, Massachusetts.