Screening tests find colorectal cancer in its earliest stages when it can be treated more successfully

Colorectal cancer (CRC) is second only to lung cancer as the leading cause of cancer-related death in the United States. In 2004, it’s estimated that CRC caused nearly 57,000 deaths.

In 2004, an estimated 147,000 new cases of CRC were diagnosed. Approximately 93 percent of colorectal cancers are diagnosed in men and women aged 50 years or older.

Screening tests can find colorectal cancer in its earliest stages when it can be treated more successfully. Screening also can identify pre-cancerous polyps so they can be removed before they turn into cancer.

A fecal occult blood test (FOBT) is a noninvasive test that detects the presence of hidden (occult) blood in the stool. Such blood may arise from anywhere along the digestive tract. Hidden blood in stool is often the first, and in many cases the only, warning sign that a person has colorectal disease, including colon cancer. FOBT can be conducted in the doctor's office or at home. In the home test, the person collects several stool samples and places the samples on special cards, and then sends the cards back to the physician or a lab to be tested. During the in-office FOBT, the physician collects a single sample from a patient during a digital rectal exam. The home test is recommended for CRC screening. The in-office FOBT is not recommended for CRC screening.

There are two types of FOBTs:

  1. the traditional guaiac smear test (Hemoccult, Seracult, Coloscreen), and
  2. the newer, flushable reagent pads (EZ DetectT, ColoCARE).

They are both useful in detecting hidden blood in the stool, and are mainly used for colorectal cancer screening.

The tests differ in the way they are performed. The flushable reagent pads are available without a prescription at many drugstores. In contrast, the traditional guaiac smear test is completed and interpreted by a medical professional, and these tests are usually available from a laboratory or a doctor's office.

Many consumers prefer the flushable reagent pads because there is no stool handling and no laboratory processing. However, health care providers usually favor the guaiac tests because the large studies that have shown the benefits of colon cancer screening were done with guaiac tests.

Between 1999 and 2000, the Centers for Disease Control and Prevention (CDC) collaborated with the National Cancer Institute (NCI) and the Centers for Medicare & Medicaid Services (CMS) to conduct a national survey of primary care physicians to examine how colorectal cancer screening and follow-up are conducted in community practice. The responses were compared with responses from the public in the 2000 National Health Interview Survey. The results indicate that physicians may not be following recommended national guidelines for performing the fecal occult blood test (FOBT) when they screen patients for colorectal cancer.

The full report is entitled "A National Survey of Primary Care Physicians' Methods for Screening for Fecal Occult Blood." It is published in the January 18, 2005 issue of Annals of Internal Medicine. To learn more about this report, visit http://www.annals.org to access the article abstract and a patient summary.

  • More than 90 percent of physicians said they ordered or performed FOBT. Although screening guidelines recommend that patients use home tests for FOBT, 33 percent of physicians said that they use only the in-office test, which is not recommended for CRC screening.

  • Studies suggest that home FOBT saves lives; to date, no studies have looked at the effectiveness of in-office tests. However, one recent study clearly showed that in-office tests miss many polyps and cancers that home tests can detect. Further, national guidelines recommend home FOBT tests instead of in-office tests.

  • National guidelines recommend that patients with positive FOBT results have an examination of the entire colon and rectum, yet about 30 percent of physicians recommend that patients first repeat the FOBT.

  • Rather than recommending that their patients with positive FOBT results have total colon exam, almost one-third of physicians recommended they have sigmoidoscopy, a procedure that examines only part of the colon and therefore can miss polyps and cancers.

  • Results from the survey of the public were consistent with these 2 findings - 1) many people reported having had in-office tests and 2) many who had an abnormal FOBT reported that they did not have a complete diagnostic work-up.

Because FOBT is often not performed or followed-up as recommended, fewer lives may be saved than is potentially possible. Patients who choose FOBT for CRC screening should use the home test. If they have positive results, they should have a total colon exam in follow-up.

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